The Effect of Scrambles on DVOA

Lamar Jackson
Lamar Jackson
Photo: USA Today Sports Images

Scrambles are pass plays, by definition. The quarterback scrambles for positive yardage when he's under pressure or when all his receivers are covered. Sometimes he runs just because a big hole opens up in the pass rush and it's going to be easy to gain yardage. But every scramble begins as a pass play. Scrambles are essentially the positive version of sacks.

Scrambles are also run plays, by a different definition. They count as rushing yardage in the official NFL stats. They are listed in the play-by-play as running plays. Here at Football Outsiders, we've always counted scrambles as running plays because they are runs in the standard play-by-play. This is left over from the way things were when I first started breaking down play-by-play way back in 2002. Back then, all quarterback runs were just runs in the play-by-play. Scrambles were not marked specifically as scrambles until 2006.

If we're looking at pass/run ratios, scrambles should count as passes, because they are called pass plays. (This is how we do it in the Strategic Tendencies tables in FO Almanac each year.) If we're looking at the decision to run or pass on certain down-and-distances, scrambles should count as passes. And when we're looking at how efficient each team is passing or running the ball, on offense or defense, we really should be looking at scrambles as passes.

It's not quite that easy, of course. Especially in this age of run-pass options, there are plays that are difficult to categorize as scrambles or "designed runs." If the quarterback makes a little pass fake on his bootleg and then pulls the ball down to run, is that a scramble? Maybe it was run all the way and the fake was just part of trying to throw the defense off its game. Does it matter how the offensive line is blocking? Is a pass a scramble if the wide receivers are all running routes, or can those be designed runs too? FO gets data from ESPN Stats & Info and Sports Info Solutions as well as the official NFL play-by-play, and there are a 30-40 plays each year where the companies will disagree on whether a run is a scramble or not.

A brief digression to show some examples:

On the play above, the NFL marked scramble, but Sports Info Solutions marked QB draw, and I think Sports Info Solutions has it right. Still, you can see how it is difficult to categorize. I think this is a run because Dak Prescott goes as soon as he hits his back foot, and Jason Witten is blocking downfield the entire time.

Is this play a scramble on an RPO, or strictly a zone read that was always a running play? The NFL marked this as a scramble. The offensive line is run-blocking, but Parris Campbell (15) is set up for a "smoke route" and then starts running downfield on a scramble-drill route.

The NFL marked this play as a run, while SIS has it as a scramble. Ryan Tannehill has pass options but runs it in when there's a big hole in front of him on the bootleg. Is that a run play or a pass play?

Despite a few plays where it's difficult to determine pass or run, it's probably a good idea to count scrambles as pass plays. Among other issues, counting scrambles as running plays sometimes gives us a skewed view of how good a team's running game is. To give just one example, the Miami Dolphins quarterbacks averaged 7.48 yards per carry this year on 40 scrambles. That ranked ninth in the NFL. On all other runs (including quarterback carries not coded as scrambles), Miami players averaged 2.94 yards per carry. That was the worst figure in the league by more than 0.4 yards.

I wanted to take a look at the effect of scrambles on each team's running numbers and what would happen if we counted these plays as passes instead of runs. So I went and re-ran this year's DVOA numbers, only this time I marked all scrambles as pass plays. This is based on the official NFL play-by-play, rather than ESPN or SIS data. Of course, the number of affected plays differed significantly for each team, ranging from just three plays (New England) to 52 scrambles (Jacksonville). The numbers are closer together on defense, but range from Miami facing eight scrambles to three different teams that faced 33.

Despite a new set of opponent adjustments, since passes and runs are adjusted separately, this new version of DVOA does not make a lot of difference in each team's total offensive or defensive rating. For over half the units in the league, offense or defense, DVOA changed by less than 0.15%. The biggest changes on offense were Denver (-0.4% less) and the Giants (0.4% more). The biggest changes on defense were Denver again (0.5% worse) and San Francisco (-0.5% better).

However, when we look at run and pass DVOA separately, some of the differences from counting scrambles as pass plays are fairly significant. Ten different teams see their rank in run offense DVOA change by at least four spots when we take out scrambles. Here's a look at old run/pass and new run/pass DVOA as well as how many scrambles each team had and the DVOA on those plays. The initial sorting order is based on the change in each team's run DVOA from the old method to the new one.

MIA -0.9% 24 -26.9% 32 3.8% 21 -39.4% 32 -12.5% 40 79.6%
BUF -0.8% 23 -3.1% 17 4.9% 20 -10.5% 21 -7.4% 43 78.2%
HOU 13.6% 15 0.0% 11 17.6% 11 -7.1% 16 -7.1% 46 76.5%
KC 43.7% 2 -1.4% 14 46.8% 3 -8.3% 18 -6.9% 23 129.3%
SEA 43.6% 4 2.7% 6 47.3% 2 -4.1% 13 -6.9% 44 95.1%
JAX 0.1% 22 -14.6% 28 2.7% 24 -20.8% 29 -6.2% 52 42.3%
TEN 29.6% 6 7.9% 5 33.9% 6 2.4% 5 -5.6% 29 125.7%
BAL 47.4% 1 21.1% 1 53.2% 1 15.7% 1 -5.4% 37 139.0%
CLE 1.9% 19 0.5% 9 5.8% 19 -4.9% 14 -5.4% 17 140.9%
NYG -4.9% 26 -5.0% 18 -1.2% 26 -10.0% 20 -5.0% 28 74.5%
CIN -12.9% 28 -9.7% 22 -9.3% 28 -14.7% 24 -5.0% 16 117.9%
GB 17.1% 11 8.3% 4 19.7% 10 3.5% 4 -4.9% 26 94.9%
DET 13.2% 16 -13.1% 26 14.9% 15 -17.5% 27 -4.4% 26 53.1%
TB 5.0% 18 -13.4% 27 6.5% 18 -17.5% 26 -4.1% 32 40.2%
WAS -18.2% 29 -11.5% 25 -14.4% 29 -15.5% 25 -4.0% 17 71.9%
PIT -18.3% 30 -22.5% 30 -16.1% 30 -25.8% 31 -3.3% 19 46.5%
DEN -8.2% 27 -6.3% 19 -6.5% 27 -9.3% 19 -3.0% 21 43.3%
PHI 10.8% 17 0.4% 10 12.4% 17 -2.4% 11 -2.8% 28 42.2%
DAL 39.3% 5 8.7% 3 40.6% 5 5.9% 3 -2.8% 19 72.0%
CHI 1.8% 20 -16.2% 29 3.2% 22 -19.0% 28 -2.8% 23 29.1%
ATL 16.3% 12 -10.5% 23 17.2% 12 -12.8% 23 -2.3% 22 50.1%
NYJ -21.9% 32 -23.4% 31 -20.6% 32 -25.8% 30 -2.3% 9 45.3%
IND -2.4% 25 1.5% 8 -0.9% 25 -0.1% 8 -1.7% 35 20.2%
ARI 1.2% 21 15.5% 2 2.7% 23 14.1% 2 -1.4% 30 37.8%
CAR -20.9% 31 2.4% 7 -19.2% 31 1.2% 6 -1.2% 25 28.6%
SF 24.4% 8 -0.5% 13 24.2% 7 -1.2% 9 -0.7% 12 23.9%
NE 14.9% 14 -2.9% 16 15.3% 14 -3.5% 12 -0.7% 3 106.3%
LAC 22.0% 9 -10.9% 24 21.8% 9 -11.3% 22 -0.4% 6 63.2%
OAK 24.9% 7 -7.3% 20 23.8% 8 -7.5% 17 -0.1% 14 9.1%
MIN 18.2% 10 -1.8% 15 17.0% 13 -1.6% 10 0.2% 8 -28.8%
NO 43.7% 3 -0.1% 12 42.4% 4 0.6% 7 0.7% 14 -13.0%
LAR 15.1% 13 -7.5% 21 14.3% 16 -6.8% 15 0.7% 10 -2.3%

Two things probably jump out at you right away. First, oh my god the Miami Dolphins. Hey, I told you that their standard running game was really bad this year, with less than 3.0 yards per carry. Change scrambles from runs to passes, and Miami's rank in pass DVOA moves up three spots. In run DVOA, the Dolphins drop from last place to even more last place. Sure, there's no ranking difference, but that drop of 12.5% DVOA is colossal. It's 70% larger than the change in run DVOA for any other team.

The second thing you notice immediately is just how good scrambles are, and the big effect of taking them out of run DVOA. This makes a lot of sense if you think about it. By definition, a scramble has to be positive yardage; even a scramble that gains zero yards is scored as a sack. But scrambles generally don't gain just one or two yards. The average for scrambles in 2019 was 7.1 yards per carry. That means we get a very high average DVOA as well. The league DVOA on all scrambles was 63.6%. Only three teams had negative DVOA on scrambles: Minnesota, New Orleans, and the Los Angeles Rams.

That also means that for 29 out of 32 teams, their new run offense DVOA (without scrambles) is lower than their original run offense DVOA. For the league as a whole, run offense DVOA drops -3.5%. I've often given the leaguewide pass and run DVOA numbers to demonstrate just how much passes tend to be more efficient than runs. It turns out that those numbers understated the efficiency advantage of calling a pass play because a whole bunch of positive called pass plays were being counted as runs. With scrambles counted as passes, the leaguewide pass DVOA goes from 10.3% to 12.3%. The leaguewide run DVOA goes from -3.5% to -7.0%. The average yards per carry (with kneeldowns removed) goes from 4.50 to 4.34.

Miami isn't the only team that gets an artificial boost to its rushing numbers due to scrambles. Seattle has the biggest change in rank, dropping from sixth in run DVOA to 13th when scrambles are removed. That's not good for a team that's so run-centric in its playcalling. Buffalo, Houston and Kansas City also drop at least four spots. And here's a surprise: Cleveland. It's a bit shocking to see Baker Mayfield with the highest DVOA on scrambles. Mayfield had 17 carries for 134 yards and 10 conversions, including converting 7 of his 10 scrambles on third down.

On the other end, the three teams with negative DVOA scrambling -- Minnesota, New Orleans, and the Los Angeles Rams -- all rank at least five spots better when we remove scrambles from running plays. The DVOA drops slightly for some offenses such as New England and San Francisco but their relative rank in run offense DVOA improves. (Tom Brady had one of the best DVOA ratings in the league when scrambling, but that's a whopping total of three plays. The big one was a 17-yard gain on fourth-and-6 from the Kansas City 29, losing by a touchdown in the fourth quarter.)

Let's run similar numbers on the defensive side of the ball:

SEA 3.9% 15 0.9% 26 7.5% 16 -5.3% 23 -6.2% 28 79.6%
NYJ 7.9% 18 -24.4% 2 10.2% 18 -30.5% 2 -6.1% 28 74.9%
ARI 20.7% 27 -11.4% 12 22.5% 27 -16.9% 7 -5.6% 29 58.2%
OAK 30.3% 30 -5.4% 21 32.3% 31 -10.6% 19 -5.1% 28 72.4%
KC -9.3% 6 4.1% 29 -5.4% 7 -0.8% 27 -4.9% 25 81.8%
IND 8.8% 19 -7.4% 20 11.3% 19 -12.1% 18 -4.7% 22 91.8%
TB -0.3% 12 -30.6% 1 1.0% 11 -35.2% 1 -4.6% 23 32.7%
CHI -4.1% 8 -11.0% 13 -1.1% 10 -15.6% 9 -4.6% 19 83.6%
CIN 24.9% 28 2.4% 28 28.0% 29 -2.1% 26 -4.5% 33 81.9%
NO 1.7% 13 -14.4% 5 3.4% 13 -18.8% 5 -4.4% 25 47.6%
CLE 7.1% 17 5.4% 30 10.0% 17 1.1% 30 -4.3% 28 81.5%
DEN 1.9% 14 -10.1% 16 5.5% 14 -13.9% 12 -3.8% 20 121.3%
PHI 5.5% 16 -18.3% 4 6.6% 15 -21.8% 3 -3.5% 21 48.4%
NYG 31.3% 31 -13.9% 7 31.7% 30 -17.4% 6 -3.5% 28 45.3%
HOU 19.5% 26 -5.1% 22 21.1% 26 -8.5% 22 -3.4% 30 51.3%
CAR -0.7% 11 18.5% 32 2.5% 12 15.2% 32 -3.3% 23 77.4%
DET 26.2% 29 -9.3% 17 27.2% 28 -12.3% 17 -3.0% 22 58.0%
ATL 17.0% 25 -10.8% 14 17.8% 25 -13.6% 13 -2.8% 28 28.0%
LAC 10.4% 20 -0.1% 25 12.5% 21 -2.8% 25 -2.7% 31 45.8%
WAS 15.8% 24 -0.3% 24 17.6% 24 -2.9% 24 -2.6% 23 63.9%
DAL 13.2% 23 -10.4% 15 13.7% 22 -12.9% 16 -2.5% 30 24.1%
TEN 11.0% 21 -12.6% 10 12.0% 20 -15.1% 10 -2.5% 33 35.2%
SF -26.3% 2 -12.1% 11 -24.6% 2 -14.4% 11 -2.3% 33 4.7%
BAL -16.0% 4 -7.9% 19 -14.1% 4 -9.9% 20 -2.1% 18 55.4%
NE -32.2% 1 -14.0% 6 -30.3% 1 -16.0% 8 -2.0% 23 39.8%
JAX 12.2% 22 9.6% 31 13.7% 23 8.0% 31 -1.6% 18 58.2%
PIT -16.7% 3 -20.4% 3 -15.7% 3 -21.8% 4 -1.4% 23 19.0%
BUF -13.5% 5 -8.3% 18 -12.2% 5 -9.5% 21 -1.2% 19 48.6%
MIA 41.5% 32 1.9% 27 41.7% 32 1.0% 29 -0.9% 8 70.6%
MIN -7.6% 7 -13.1% 9 -7.3% 6 -13.5% 14 -0.4% 9 26.3%
LAR -1.3% 9 -13.6% 8 -2.5% 8 -13.3% 15 0.3% 22 -38.3%
GB -1.3% 10 -0.8% 23 -1.5% 9 -0.3% 28 0.5% 24 -14.3%

The Seattle running game looked worse when we removed scrambles, but the Seattle run defense looks better because the Seahawks defense was one of the league's worst against scrambles. The Jets and Bucs run defenses look even more stellar when we don't count scrambles as runs. On the other side, the Rams and Packers are the only teams with negative DVOA allowed on scrambles, so their run defenses look worse when scrambles are removed. The Rams' run defense DVOA barely moves, but because of the run DVOA dropping around the league, their rank in run defense goes from eighth to 15th without scrambles.

Where do we go from here? If we want, we can probably switch over to start counting scrambles as pass plays in team DVOA starting in 2020. However, there admittedly a couple of issues if we want to always treat scrambles as pass plays.

First, there's a lot of hard work to re-run all 35 seasons of DVOA to change scrambles from runs to passes. And what do we do about the seasons before 2006 when scrambles were not marked in the play-by-play? It helps that option plays were so much rarer in the NFL 20 years ago. One possibility is to simply mark all quarterback runs as scrambles except for probable quarterback sneaks (third-and-1, fourth-and-1) and runs for a loss (which can't be scrambles, since a scramble for negative yardage is technically a sack). This would be an imperfect solution but might be closer than counting scrambles as runs for measuring the "real value" of passing and rushing for each team.

It's also a lot easier to change scrambles in team DVOA than in individual DVOA for quarterbacks. For team DVOA, all plays use the same baseline -- that's why the leaguewide pass DVOA is higher than the leaguewide run DVOA. For individual DVOA, passes and runs have different baselines, and runs have different baselines based on player position. So changing our individual stats would involve a lot of work figuring new baselines, whether that would be turning scrambles into pass plays or just combining all quarterback plays into one number no matter whether it's a run or pass.

All of these issues are under consideration, but it's clear that how we treat scrambles does change how we measure pass and run games separately.


38 comments, Last at 18 Feb 2020, 4:27am

1 I am in favor of changing…

I am in favor of changing scrambles to pass plays, even with some of the murkiness that introduces noise to the data.

I am curious how predictable scramble dvoa is year to year and how much added value it brings relatively speaking. It would gives us a nice sense of the tradeoffs between qbs who never scramble and never get sacked(Drew Brees) vs the opposite(Fitzpatrick i guess?)

36 If you include retired…

If you include retired players, Peyton Manning is probably the ultimate "never scramble/never sacked" QB. Led the NFL in lowest sack rate five times, but averaged only 2.5 rushing yards per game in his career. In four years in Denver he ran for -55 yards. Obviously that's a lot of kneeldowns, but from between 2013 and 2014, Manning passed for over 10,000 yards, with exactly two carries that gained positive yardage (a 1-yard touchdown in 2013 and a 4-yard gain on second-and-10 in 2014). 

37 Actually, Marino has Manning…

Actually, Marino has Manning beaten (badly, in fact) in both categories.  Marino led the league in lowest sack percentage 10 times, and even more amazingly, only ran for a total of 87 yards (not a typo) in 242 games.  He only had positive rushing yardage in 5 of his 17 seasons!

2 Scrambles

The only thing I have to add is that in the 3rd to last paragraph, you might check any carries around the goal line. I remember a naked bootleg that PM ran that fooled the cameras, and I think I remember a TB one too. Also, I don't know how the NFL would have labled QB draws in the past. Certain QB's who are faster/more mobile run them more often than others, but IMO those should be considered QB runs.
I would also think that you could have a QB run go for negative yardage if it seems to be a run from the get-go--like some of Cam Newton's/Lamar Jackson's runs.

3 It's weird to me that…

It's weird to me that scramble DVOA is so high. 7.1 yards per attempt is high, but the baseline for a pass is 6.3. 7.1 yards per attempt makes you Oakland (25%).

14 At a guess, a…

At a guess, a disproportionate number of scrambles must occur on third down (and result in conversions.) 

You can imagine many scrambles where the QB slides or goes out of bounds as soon as they are past the marker. So the yards per attempt is slightly suppressed, but the success rate is very high. 

21 Some thoughts on why this…

Some thoughts on why this could be the case:

1) DVOA in general has never correlated well with YPC/YPA due to situational factors. For example, a gain of 15 yards on 3rd and 20 isn’t particularly valuable for DVOA, and a gain of 40 yards in that scenario (assuming it doesn’t result in a touchdown) isn’t all that much more valuable than a gain of 21 yards.

2) Avg. yards per scramble might be artificially suppressed by coaching decisions, i.e. QBs are being taught to protect themselves once they gain a first down rather than risking injury to squeeze out a few extra yards. 

3) QBs not known for their scrambling prowess might only attempt to scramble in critical situations and when it’s highly likely to produce a first down. This would increase the rate of successful scrambles relative to successful passing plays and impact DVOA.

4) Certain negative outcomes that passing DVOA penalizes, such as interceptions, aren’t possible when scrambling.

27 Number 3

Number 3 is definitely true. I can run some numbers if I do something more on scrambles, but the conversion rates are very high.

4 I encourage putting…

I encourage putting scrambles into passing instead of rushing. As for handling before 2006, I'd look at 2006 on and then see if pre 2006 numbers are weirder than post 2006 numbers using the simple assumptions.

6 Should scrambles just be its…

Should scrambles just be its own category? When Miami changes from basically a 0 DVOA throwing the ball, to a +4 DVOA "passing", it seems like the scrambles are changing the story with regards to Miami's actually ability to move the ball through the air. It looks like Miami scrambled between three and 52 times, which would likely represent less than 10% of their pass plays, but those plays seem to have an outsized effect on their passing DVOA.

Though I know having too many categories can sometimes just muddy the water as well. I've always thought baseball should count inside-the-park HR's as "quadruples" since they tell a different story from a guy who hits a ball over the fence. But they are rare plays, so maybe not worthy of their own category.

25 Bigger question: should we…

Bigger question: should we even have any categories? Or maybe better put: why are we using the NFL's silly gamebook grouping at all?

I mean, certainly if you look at a team's rushing performance and passing performance separately, they're clearly not independent. There's a strong correlation between the two (by DVOA, there's like an r-squared of ~0.2, which is pretty damn high considering how noisy DVOA is, period). So if they're not actually giving us independent information, why are we bothering to group them separately at all?

I can list a bajillion problems grouping plays like this. Screens aren't pass plays. Shovel passes aren't pass plays. And then on the defense, it just keeps going. If a team's got 9 guys near the line of scrimmage to stop a short-yardage run and the other team fakes them out and tosses a 2 yard pass that goes to the house, how is that counted as pass defense when they weren't playing pass defense?

I mean, shovel passes expose how ludicrously stupid this grouping is, don't they? If a quarterback sticks the ball forward and a guy takes it, it's a run. If, instead, he puts a teensy bit more oomph and it goes into the air and the guy catches it, it's a pass.

It's silly. We've got Next Gen Stats player tracking and ESPN's got a machine learning-based system which can identify defenses in real time, and we're grouping plays together based on ideas from the 1930s.

26 If I am remembering…

If I am remembering correctly, DVOA is probably agnostic about the play type, its just about the result. 


I think dvoa gets broken into components for a number of reasons. For one, it lets us compare matchups across units between teams. Like pass O vs Pass D. 


Second, people like to see how the individual components measure up vs just dvoa. 

7 It looks like a lot of work...

but you could put Bryan and Andrew on it, they being intrepid scramblers, Scramblenistos, Scrambleneers, Scrambletons, Scramblesatians, Scramblenauts, etc., etc.

9 Aaron, are you certain that …

Aaron, are you certain that "scrambles for negative yards are technically sacks" (or maybe I'm misunderstanding).

Looking at this game:

There is a play in the first quarter that says: (6:03) L.Jackson left end to CIN 13 for -1 yards (J.Tupou).

Yet the gamebook says that Baltimore was sacked once in the game for an 8-yard loss. So it looks like there are times when the statistician will make a determination if the QB had become a runner by the time he was tackled?

15 The NFL defines a loss of…

The NFL defines a loss of yardage or no gain to be a sack based on whether a player "makes an attempt to pass at any time." I mean, we're trying to measure the effectiveness of pass rush/pass defense here, right?

24 Just following along on the…

In reply to by Aaron Brooks G…

Just following along on the thread (not sure of the exact wording anywhere) but he said definition of a sack. Your Brees example is past the line of scrimmage so the possibility of a sack does not even exist, making the pump fake, in the context of the argument you two are having, irrelevant.


19 I thought scrambles were running around behind LOS

When I think of scramble, I normally think of Tarkenton, who logged a plethora of miles running around behind the LOS but mostly with intent to keep running until he found a target to throw to. He did run some (and retired with the career rushing yardage by a QB at the time, many times since broken by people who played far less time), but his main goal in scrambling was to eventually throw the ball. I'm not sure how you quantify that short of having some kind of positional time data... plays like this one...

20 Good work.

Good work. It's nice to get a feeling for how big this effect is.
I'd vote for marking all scrambles as pass plays. I can see that there are going to be plays that are hard to categorize. That's okay. Just do your best.

23 I've kicked around the idea…

I've kicked around the idea that as protections for QBs have increased, a trade-off is demanded. My thought was that it would be illegal for a QB to cross the line of scrimmage until a play was down. This would eliminate QB sneaks, runs, and scrambles.

28 I've also thought about…

I've also thought about trading off QB protections and other changes that have made the passing game relatively more effective.  My pet rule change is to make the definition of a forward pass any pass that is caught or falls incomplete beyond the line of scrimmage.  That means any pass caught or that falls incomplete behind the line of scrimmage is a live ball / fumble.  It would have some cool properties:

  1. You get penalized for hitting the QB, but now a pass batted at the line is worth more to the defense.  You can play for the bat sometimes instead of always the sack.
  2. Jet sweeps where the QB does a 6" touch pass as the WR runs by are now officially running plays.  Also if you mess up the exchange it's a live ball, not incomplete.
  3. WR screens / "now" passes are also officially runs.  If the WR doesn't catch the ball, it's a live-ball fumble.
  4. Screen passes are officially runs.  If the defense blows up your screen and the QB spikes the ball at the feet of the RB, that's a live ball.
  5. If a QB tries to throw the ball away and it doesn't make it to the LOS, that's a live ball not intentional grounding.

The super safe parts of the passing game become riskier to the offense, but not necessarily riskier for the QB or players.  Also, if you can't tell, I like fumbles and turnovers.  This could balance out the huge drop in interceptions somewhat and make turnovers a bit more likely.

29 I'm ok with most everything…

I'm ok with most everything except the battle ball becoming live. Idk how many battle balls occur per possession, but a fumble is one of the costliest outcomes for a team and such a change would dramatically alter the risk reward nature of passing

31 Imagine having to stage a…

Imagine having to stage a replay review after the QB threw a deliberate bounce pass to a wide out 2 yards past the line, to determine if the ball hit the ground behind the line (thus a legal bounce pass) or past it (and incomplete).

34 Imagine having to stage a…

Imagine having to stage a replay review after the QB threw a deliberate bounce pass to a wide out who was even with the QB behind the line of scrimmage, to determine if the ball hit the ground at or behind where he released it (thus a legal bounce pass) or in front of it (and incomplete).