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21 Jul 2004

Press Check: Pass Interference Changes

by Aaron Schatz

This article was originally written in July 2004. One year later, I wanted to re-visit it and how accurate it turned out to be. The 2005 updates are in this purple, italicized font.

In our "Extra Points" article blog last week I linked to a long piece by ESPN.com's John Clayton discussing this year's change in the way referees will be calling pass interference.  In a reaction to the public mauling given the Colts by the Patriots during the AFC championship, the league wants to clamp down on defensive backs holding and obstructing receivers after five yards.

We keep referring to it as a rule change, but it isn't actually a rule change.  According to the Competition Committee, they are only asking referees to enforce the letter of the law, as it was changed in 1994.  They tossed a few extra words to hammer the point home, but the rule is the same.  As Clayton writes:

The intent of the 1994 "chuck" revision was violated. Out goes the word only and into the rule book goes language that tells defenders not to restrict or impede a receiver "in any way." Defenders can get away with incidental contact but not get away with any intentional contact. 

So, will this change anything?  Nobody can be sure, really.  While it is possible that this rule change will really boost passing this year, I think what is more likely is that the rule will be heavily enforced in the preseason and the first couple weeks, but gradually the referees will revert to the way they have called things in the past, or close to it. This is what seems to happen every time baseball changes its strike zone, for example.

However, if they really do crack down on physical play by cornerbacks, Clayton feels that the results will be similar to the increase in passing that took place in 1994, the last time they tried to call pass interference in this strict fashion.  His article also speculates on what the change will mean for the NFL as a whole as well as individual receivers.

So, Clayton's statements seem pretty easy to test.  If

a) John Clayton says that the change from 2003 to 2004 will be like the change from 1993 to 1994, and

b) John Clayton says that X, Y, and Z are likely to happen in 2004

then it is probably a good idea to go back and see whether X, Y, and Z happened in 1994.

(Those of you who have a long memory may recall that Bill James did this exact same exercise in his 1988 Baseball Abstract when baseball threatened to call the strike zone "by the book" just like they had in 1963.  He went back, figured out what kinds of players improved or declined between 1962 and 1963, and used that as a guideline for which players were likely to improve or decline in 1988.)

Now, of course, if the changes this year are different from what they were in 1994 -- or if the referees don't really change the way they call pass interference at all -- none of this really makes any difference.  But for now, let's assume Clayton is right, that the changes in the game this year will match those between 1993 and 1994.  Given that idea, how on target are his predictions?

If you want to skip all the specifics, there is a summary at the end.

Clayton: "Some people you talk to tell you the impact will be minimal. Those are the same people who misjudged the impact of Charlie Weis's short passing offense on the opening years of the new millennium."

Really?  The exact same people?  Like, the same five guys or something?  Is one of them Merril Hoge?

Clayton: "Go back to 1994 when the rule was put in. Passing yardage went up a total of 26 yards per game (from 401.2 to 427.2, second highest in the modern era). Average completions went from 11.6 to 11.7. Average attempt went from 5.8 yards to 6. Scoring went from 37.4 to 40.9 per game."

Clayton is partially right here, and partially wrong, and I'm also partially confused.  I used Doug Drinen's pro-football-reference.com for my statistics and the numbers for passing yards per game and average yards per attempt are different from the numbers Clayton is giving.  I'm not sure where the disconnect lies -- perhaps in how the two sources consider sack yardage? -- but let me go through these numbers to see if they are accurate.

Passing yardage per game did in fact go up from 1993 to 1994.  In Drinen's numbers, the increase is a bit smaller, from 430.8 yards per game to 454.8 yards per game.  Clayton likes to give stats per game that combine both teams, which isn't really how I generally think of "per game" statistics, and these numbers make the changes look greater than they really are.  If I told you that passing went up by 24 yards per game, that sounds more impressive than telling you passing went up by 12 yards per game.

But while Clayton is right about total passing yardage increasing in 1994, his numbers for yards per pass are misleading.  First of all, I should point out that Drinen's numbers for yards per attempt are different than Clayton's.  He has yards per attempt increasing from 6.7 to 6.8 instead of 5.8 to 6.0.  Either way, that's a very small change -- and, when you look at more than just two years of data, it clearly represents normal variation, not a trend towards more success in the passing game.  Here are the passing game numbers for the three years before and after the rule change (giving the average per game for one team, not two):

Passing per game, per team Comp Att Comp% Yds Yd/Att Yd/Comp TD INT
1991 AVERAGE 17.9 31.1 57.4% 214.5 6.89 12.01 1.14 1.09
1992 AVERAGE 17.2 29.9 57.5% 205.4 6.86 11.94 1.15 1.16
1993 AVERAGE 18.6 32.2 57.9% 215.4 6.69 11.55 1.15 1.05
1994 AVERAGE 19.5 33.6 58.0% 227.4 6.77 11.66 1.30 1.06
1995 AVERAGE 20.2 34.8 58.2% 235.6 6.77 11.64 1.38 1.07
1996 AVERAGE 19.2 33.3 57.6% 222.2 6.68 11.60 1.30 1.13
1991-1993 AVERAGE 17.9 31.1 57.6% 211.8 6.81 11.83 1.15 1.10
1994-1996 AVERAGE 19.6 33.9 58.0% 228.4 6.74 11.63 1.33 1.08

Any increases in the passing game after the 1994 rule change came from more total passes, not more success on each pass.  Yards per attempt and yards per completion were actually lower when you compare three-year periods rather than just the years 1993 and 1994.  Completion percentage and interceptions per game stayed roughly the same.  The difference came from 2.8 more passes per game, probably thanks to a few more first down opportunities that arose from the separate penalties.  To me, this looks like nobody really played any differently after 1994.  The refs may have been calling a few more pass interference penalties, but it didn't really help players catch passes more often or for more yardage.

(If you are curious, rushing numbers were pretty much the same before and after the rule change.)

2005 Update: Clayton turned out to be right, but it is difficult to tell whether the increase in offense had anything to do with the enforcement of illegal contact because, as this article points out, offense has been trending upwards for a few years. Scoring was up from 2003, but no higher than 2002. Yards per attempt were at their highest since 1989, but yards per completion just returned to the level of 1997-1999. The rate of passing touchdowns per game was the highest in history, the rate of interceptions per game was the lowest.

Clayton: "More teams will have the ability to pass for 4,500 yards. Games will be higher scoring."

Yes, this is what happened in 1994.  From 1991-1993, teams averaged 18.8 points per game.  From 1994-1996, teams averaged 20.7 points per game.  If this happens again this year, though, is anybody going to notice?  If your favorite team is suddenly kicking an extra field goal every other game, how long will it take you to realize something is different?  As for 4,500 yards, as I noted above, total yardage numbers went up even if yards per pass did not.  Before 1994, less than one team a year threw for 4,500 yards.  Three hit the mark in 1994, four in 1995.  Of course, by 1996 it was back to zero again.

2005 Update: Scores only went up slightly, but wow, more teams certainly did have the ability to pass for 4,500 yards. What made 2004 remarkable is less the level of offense and more the standard deviation, with lots of really good quarterbacking and lots of really bad quarterbacking. Five teams passed for 4,500 yards (IND, MIN, KC, STL, GB) after none did in 2003 and only Oakland did in 2002.

Clayton: "Veteran receivers who get quickly into routes -- Marvin Harrison of the Colts and Isaac Bruce of the Rams for example -- should have monster years."

I'm not sure what defines "getting quickly into routes" but we can go back and see if any veteran receivers had monster years in 1994.  26 receivers went into 1994 with at least five seasons experience and back-to-back years of at least 500 yards receiving.  On average, these receivers dropped by 48 receiving yards compared to their average in 1992 and 1993.  To me, that sounded like an average year, like nothing really special happened in 1994.  But, just to make sure, I decided to see what happened to the receivers from 2003 who fit the same requirements.

Even though I just wrote a long article on a set of wide receivers who declined in 2003, the result still caught me by surprise.  25 receivers went into last year with at least five seasons experience and back-to-back years of at least 500 yards receiving.  On average, these receivers dropped by 246 receiving yards compared to their average in 2001 and 2002.  Seven of these veteran receivers in 1994 had at least 250 yards more than they had averaged the two seasons before.  Only two receivers last year could say the same: Randy Moss and Keenan McCardell.

It sounds like the rule changes really had a strong effect until you realize how many of these receivers really took their big step forward in 1993, the year before the rule change, and not in 1994.  Tim Brown, for example, finally blossomed in 1993 after the Raiders stopped futzing around with Todd Marinovich at quarterback.  Cris Carter finally put it together in 1993 after screwing around for his first few seasons in Philadelphia.  Irving Fryar got traded in 1993 from the Hugh Millen-led Patriots to the Dan Marino-led Dolphins.  Each of these receivers had a bigger gain in yardage in from 1992-1993 and then a smaller gain from 1993-1994.

The next two veterans who had big steps forward in 1994 are connected.  Henry Ellard left the Rams for the Redskins and ended up having his second-best year in his twelfth NFL season.  He went from 945 yards in 1993 to 1397 yards in 1994, and enjoyed two more 1000-yard seasons before retiring after 1998.  With Ellard gone, Flipper Anderson became the number one receiver with the Rams and went from 552 yards to 945.  This was a total fluke and probably had nothing to do with any rule changes.  Somebody had to catch the ball for the 4-12 Rams.  Anderson had only eight more catches his whole career.

The sixth receiver in the group was Quinn Early of the Saints, who had 566 yards in 1992, 670 yards in 1993, and 894 yards in 1994.  That's nice but not really a "monster year."

The receiver who may best represent what Clayton thinks will happen with Harrison and Bruce is Andre Reed of the Bills.  After 913 and 854 yards in the previous two seasons, Reed caught 90 passes for 1303 yards in 1994, fifth in the league and second-highest in his 16-year career.  Unfortunately, it is hard to tell how much of a fluke this was because Reed got injured the following year and played only six games.  Also, if I was a Ram or Colt fan this isn't really the example I would want my favorite receiver to follow.  Reed had that great year but the Bills as a whole collapsed to 7-9 after four straight AFC titles.

Hmm, this is starting to go on a bit, isn't it.  OK, as for the other veterans, I can tell you there were plenty of receivers who had years in lines with their last few seasons (Jerry Rice, Anthony Miller, Andre Rison) and a few guys who collapsed as veterans sometimes do (Mark Jackson, Eric Martin, Anthony Carter).

If 2004 does turn out like 1994, what will likely happen is that the decline phase of some veteran receivers will slow down a bit, and a couple of them will have big seasons out of line with what they've done the last two years.  For most of them, though, things won't be any different than if there had been no rule change.  As for who is most likely to suddenly have an Andre Reed season, can you name this wide receiver?

  Year Season Catches Yards TD
Andre Reed 1992 8 65 913 3
Andre Reed 1993 9 52 854 6
Player X 2002 8 53 906 2
Player X 2003 9 56 854 5

That current wide receiver whose last two seasons are eerily similar to the ones Andre Reed had at the same age is Eddie Kennison.

2005 Update: Bingo. Eddie Kennison had his first 1,000-yard season in 2004. Numerous receivers above the age of 30 had big seasons, led by Terrell Owens, Muhsin Muhammad, and Joe Horn.

Clayton: "Maybe this is just judgmental, but I believe rookie receivers will have more impact in their first seasons."

On the other hand, if we use 1994 as a guide, some rookies are really going to feel the effect.  From 1991-1993, only three rookie receivers taken in the first two rounds of the draft had at least 500 receiving yards.  In 1994 alone, three rookie receivers taken in the first two rounds of the draft had at least 500 receiving yards.  In fact, two of these receivers had more yards in 1994 than any rookie receiver of the previous four years: Darnay Scott (868 yards) and Derrick Alexander (828 yards).  Then, in 1995, Joey Galloway had the first 1000-yard season of any rookie receiver since Bill Brooks with the 1986 Colts.  (As an aside, Brooks may have been the most unexpected rookie receiving star of all time; he was a fourth round draft pick from a school, Boston University, that doesn't even play football anymore.)  And 1996, of course, was 1996.

In total, eight rookie receivers from 1991-1993 topped 500 yards.  18 rookie receivers from 1994-1996 topped 500 yards.  Of course, correlation does not mean causation, and there are plenty of other possible explanations for why rookie receivers were so much better after 1994.  But if you believe that the pass interference rule changes will make 2004 much like 1994, rookie wideouts are going to have much better seasons than we expect.  Good news for everyone who took a wideout in the draft -- and perhaps another reason to hop on the Jacksonville and Detroit bandwagons.

2005 Update: Right idea, wrong receivers. It was a huge year for rookie receivers, just not the ones from Detroit or Jacksonville. Michael Clayton had an astonishing season, one of only two receivers to rank in the top 10 in DPAR since 1998. (The other? Randy Moss.) Lee Evans and Larry Fitzgerald were very good as well. Roy Williams was good until he was hobbled by injuries.

Clayton: "Defenses will use more blitzing packages to put pressure on quarterbacks and force quicker throws... Sacks fell to 1,092 last year, lowest since 1994. Watch the sack numbers increase."

Unfortunately, I only had enough time to total the sack numbers for 1993 and 1994 (actually, Mike did it for me).  There were 1,055 sacks in 1993 and only 936 sacks in 1994.  As Clayton notes above, that's the lowest total for the last decade.  If sack totals went down last time the NFL fiddled with the pass interference rules, I'm not sure why they would go up this time.

2005 Update: Clayton wins, sort of, as sacks did in fact go up in 2004. There were 1196 sacks compared to just 1092 in 2003. But there were also 1196 sacks back in 2001, with only 31 teams, and more than 1200 sacks in 1999 and 2000.

Before we go, there was one prediction that Clayton didn't make, but many people are making it.  After what they did to the Indianapolis receivers in the AFC championship game, it's pretty clear that this rule change is aimed, in part, at the Patriots.  So let's figure out what happened to the top defenses of 1993 when the rules were changed.

Lots of people but not Clayton: "This rule change will hurt defenses that depend on physical play from their cornerbacks." (If you are a Colts fan, add: "and cheat all the time")

Didn't happen in 1994.  In terms of yards allowed per pass attempt, the top four pass defenses in 1993 were Dallas, Green Bay, Chicago, and San Francisco.  In 1994 they were all still in the top six.  The fifth-best pass defense of 1993 was Kansas City; they were average in 1994, but that wasn't because the rules had gotten harder on their defensive backs, that was because their defensive backs all left town (Kevin Ross to the Falcons, Bennie Thompson to the Browns).

The number one defense in 1994 in terms of yards allowed per pass attempt was the Cleveland Browns.  They were coached by some guy named Bill Belichick.

2005 Update: Yep, sure slowed down the Patriots, didn't it?


We don't really know what effect the change in pass interference guidelines will have this year.  However, if the effects are similar to the last time these rules were strictly enforced, back in 1994, here's what you can expect:

  • Passing yardage and pass attempts will increase.  The average team will pass for 10-15 yards more per game.
  • Scoring will increase slightly.
  • However, the effectiveness of individual passes won't really change at all.  We'll just see a few more of them.
  • A few veteran receivers will see their aging patterns slow a bit.  A couple may have unexpected 1000-yard seasons.
  • Rookie receivers will likely have a greater impact than in past years.
  • The rule changes won't affect defenses with physical cornerbacks (New England, Miami) any more than the rest of the league.

Posted by: Aaron Schatz on 21 Jul 2004

8 comments, Last at 13 Jun 2005, 5:33pm by Jeff F


by charles (not verified) :: Sun, 06/12/2005 - 8:49am

RE: 56
Why be shocked, you don't need high round draft picks in your secondary to play off-coverage, zone, and to knock down receivers in the red zone which is what the patriots do. Not to knock how the patriots play defense but it's similar to how the broncos run block. They both use physical and borderline illegal tactics to be effective. The positive is that anybody who is smart enough to know the plays can be used in these systems.

by Jeff F (not verified) :: Mon, 06/13/2005 - 12:03am

charles - Your comment sounds like it comes from before the 2004-2005 season. The Patriots clearly dealt with the rule change, and managed to destroy the Colts in the playoffs again, without pushing the rules to the limits, as they did in 2003.

by charles (not verified) :: Mon, 06/13/2005 - 1:56am

RE: 60
Ok, i'll try to rephrase so not to discount the patriots accomplishment. IMO, When the colts and patriots play each other, both teams bend the rules when it comes to illegal contact. As a matter of fact every team in the nfl bends the rules when it comes to illegal contact if they are trying to win the game. Why the patriots are so much better at jamming recievers than the colts I don't know maybe somebody can tell me. But the point i'm making is that the better pass defenses in the league bend the rules when it comes to illegal contact. That includes the dolphins, bucs, patriots, eagles, redskins, steelers, bills etc.

by Purds (not verified) :: Mon, 06/13/2005 - 9:40am

re: "Why the patriots are so much better at jamming recievers than the colts I don’t know maybe somebody can tell me"

Well, that's easy. While everyone spent the year falling over themselves to praise the Pats defense because they had to play unknowns in the defensive backfield, the Colts had at least as unheralded a crew back there, and they didn't have the linebackers or defensive front to compensate. In almost every game, the Colts had at least 3 of the 4 CB's and safeties who were rookies (Sanders, David, Hutchinson) or second year players (Doss). That's why the Colts couldn't jamb very well. That, plus the Colts' mediocre LB play, and you have a lot to worry about as a Colt defensive player.

by Mr Shush (not verified) :: Mon, 06/13/2005 - 11:10am

But that doesn't explain why the (equally inexperienced) Patriots CBs jam better than them - just why it matters less when they do screw up.

by B (not verified) :: Mon, 06/13/2005 - 11:28am

Jamming is only effective if you can get pressure on the QB quickly. Otherwise, the receivers can fight off the jam and get open, or the db is forced to hold well past the 5 yard buffer zone.

by Purds (not verified) :: Mon, 06/13/2005 - 5:28pm

re: #63

The Colts couldn't take the risk to jamb with inexperienced backs and linebackers. The Pats, on the other hand, could take the risk in the back, knowing they were solid at LB and on the line. That's my point -- the rest of the Pats D allowed the DB's to take risks. The Colts D, as you well know, wasn't good enough to take risks anywhere.

by Jeff F (not verified) :: Mon, 06/13/2005 - 5:33pm

Charles - if you wuld have been around here more often, you would have seen some pretty good analysis on why their defense was still so effective. First, the Patriots secondary at the end of the year was still very good. They have a pair of excellent safeties that compliment each other very well (Harrison is more physical, better against the run, Wilson is fantastic in coverage). Asante Samuel is a decent CB, and Randall Gay is about as good as you could expect an undrafted rookie to be, there are some teams he would be a starter on, and many where he'd be the nickel back. Earlier in the season, when they had Earthwind Moreland, Randall Gay, and Troy Brown as the nickel back, you might have noticed that against teams like Cincinatti and KC, their secondary was very, very ineffective (I was at the game against Cinci, and the defense looked downright sad that game). But, name one other position they are weak at. You can't, really, they have an extremely good core of lineman and linebackers, a pair of excellent safeties, and a servicable pair of CBs. The LBs can rush to provide pressure, or drop back in a very effective zone defense.

The importance of the CBs in the Patriots more recent games is simply less than it has been in the past. Bellichick and Crennel didn't expect a Law-like performance out of Gay, so they gave him less to do. He can jam the receivers up front a bit, and Eugene Wilson is behind him, and is expected to pick up the route.

The real problem with the Patriots defense is when Wilson is injured. Dexter Reid just can't keep up. Randall Gay would do his thing, but Reid wouldn't pick up coverages he was supposed to, and that's how it has looked like Randall Gay was at falut for letting a receiver run by him, whereas in fact Reid was the problem, as he had the tougher job to do, as the lack of Law had been dealt with, but there was no effective way to deal without Wilson.

So, how did the Patriots destroy the colts again? They showed blitz on almost every down. This led Manning to audible to a safer play that would be able to handle a blitz. But the blitz never came. Well, they rushed 5 ONCE in the entire game. The rest of the game, the Patriots were rushing 4 or even 3 men! If you only have 3 men rushing the QB, you have an extra man in coverage. This makes it a lot easier to shut down the passing game, especially if even only three linemen can provide some pressure to the QB, which they were. In the many cases where the Patriots were providing adequate pressure with 3 men rushing, that provides them with an advantage comprable to letting them have 12 men on the field. Only they only had 11. The lightweight Colts offensive line just wasn't enough.

So, the Colts offensive line was more of a reason that their WRs couldn't get open, the Patriots had too many guys in coverage, and were still getting a decent pass rush, and they were completely shutting down the Colts' rushing game, to boot. How can you expect to beat a team that is dominating you so badly that they can rush 3 men, stifle your running game, providing pass pressure, and have guys plastered all over the field if you decide to throw the ball, all while showing formations and motion as if they are going to blitz 5 guys, who would completely trample over the offensive line and cause sacks if you weren't prepared?

It's simple. You can't. The Steelers destroyed the Patriots earlier in the season when the Pats offensive line was dominated six ways to sunday, and that was a large part of the reason why they won the game. The Patriots did the same thing to the Colts in Foxboro.