ALEX: 2017 Season Review
by Scott Kacsmar
Perhaps blame it on a rash of big-name quarterback injuries, but the 2017 NFL season did not continue the trend of new passing records being set league-wide. The completion percentage (62.1 percent) and sack rate (6.4 percent) dipped to their lowest marks since 2013, and the interception rate (2.5 percent) was higher than it had been in the previous two seasons. (Thanks, DeShone Kizer).
As for throwing short of the sticks on third down, which is what ALEX looks at, that also fell to its lowest level since 2009. In this case, the lower number means the shorter the pass is traveling relative to the marker. The league-wide ALEX was +1.1 this year, matching the last low of +1.1 in the 2009 season. At least things picked up from the +0.7 that we observed through Week 4 this year.
For those new to this metric, it is called Air Less EXpected, or ALEX for short. ALEX measures the average difference between how far a quarterback threw a pass (air yards) and how many yards he needed for a first down. If a quarterback throws a pass to a receiver 4 yards behind the line of scrimmage on third-and-13, then that would be -17 ALEX. The most meaningful ALEX numbers come on third and fourth down, when it's really crucial to get 100 percent of the need yards to extend the drive.
This is a review of the regular-season results, and as always the numbers are subject to change after we clean the game charting more in the offseason. We will look at both defenses and quarterbacks for the 2017 season.
Defenses: 2017 ALEX Rankings Through Week 17
The following numbers are for third down only. Since this is defense, the teams are ranked from lowest to highest for the various stats. Lower DVOA is better. A lower ALEX means the defense is keeping the play short of the sticks. Short% is the percentage of third-down attempts that were thrown short of the sticks (negative ALEX). ALEX and Short% generally have strong correlation (typically near -0.850), but Short% is a good way to account for outliers.
|2017 Defenses: Third-Down ALEX Splits|
|Rk||Team||ALEX||2016 ALEX||2016 Rk||CONV%||Rk||DVOA||Rk||Avg. Need||Rk||Short%||Rk||Passes|
|Rk||Team||ALEX||2016 ALEX||2016 Rk||CONV%||Rk||DVOA||Rk||Avg. Need||Rk||Short%||Rk||Passes|
The correlation between ALEX from 2016 to 2017 was up to 0.36, but we are used to seeing defense fluctuate from year to year. However, 2017 was a bit more consistent on that front as 12 of the top 16 defenses in 2016 ALEX were in the top 16 again this season. Houston had the biggest fall from fourth to 28th, but that defense was ravaged by injury this year, especially when J.J. Watt and Whitney Mercilus went down in the same game. Washington's quiet defensive improvement shows up here too as the Redskins climbed from 17th in ALEX to fourth, and the unit finished third in conversion rate, fourth in DVOA, and first in Short%. In 2016, the Redskins had the worst conversion rate and DVOA on third-down passes.
The Eagles and Falcons will meet in the playoffs on Saturday, in a collision of the top two defenses in ALEX . Atlanta actually forced the most average need yards (8.5) on third-down passes this year, but the Eagles were third (8.3). Atlanta's rank of seventh in conversion rate and 25th in DVOA is the largest difference in 2017. Part of this is because the Falcons were often thrown against in favorable situations, and still allowed too many conversions. In general DVOA this year, the Falcons ranked 27th on third-and-medium and 29th on third-and-long.
One defense that seemed to shine on third down no matter how many yards were needed or how far the ball was thrown was Minnesota. The Vikings ranked first in conversion rate (26.6 percent) and by far first in DVOA (-35.4%). In fact, since the NFL started officially tracking third-down conversions in 1991, the 2017 Vikings had the best season yet with a conversion rate of 25.2 percent (for all third downs, including runs). They'll get a great test this weekend with Drew Brees and the Saints, but this is a defense that the Vikings can ride to a Super Bowl.
When we get a chance to put together ALEX numbers on defenses for several seasons, I would like to see how it correlates with pressure rates. We mentioned Washington's stark improvement, and it probably isn't a coincidence that the Redskins ranked first in pressure rate (37.7 percent), according to Sports Info Solutions (subscription required). Meanwhile, the Buccaneers were dead last in pressure rate (26.6 percent), and were also 32nd in ALEX (+3.1) and 32nd in conversion rate (49.7 percent). Dirk Koetter is getting one more chance in Tampa Bay, but some other coaches on teams that allowed a high rate of conversions are not so fortunate. John Fox (28th-ranked Bears), Chuck Pagano (29th-ranked Colts), and Jack Del Rio (30th-ranked Raiders) all got the boot, and the 31st-ranked Packers finally relieved defensive coordinator Dom Capers of his duties.
Quarterbacks: 2017 ALEX Rankings Through Week 17
The following table looks at every quarterback this season with at least 50 third-down passes through Week 17. The quarterbacks are ranked from highest to lowest ALEX.
The correlation between ALEX and conversion rate was 0.36, or the lowest in three years. Much like with performance under pressure, any time YAC and broken tackles are involved, the game can get pretty unpredictable. We also had some unsavory quarterbacks making the cut this year, including three different passers for the 49ers.
Aaron Rodgers barely made the cut thanks to his collarbone injury, but he led all passers in highest ALEX (+4.0) and lowest Short% (21.6 percent). Rodgers actually threw the third-shortest passes in the NFL this season, but on third down, he was still as aggressive as anyone. He has ranked in the top six in ALEX in every season since 2008. Brett Hundley tried to replicate Rodgers' strategy, ranking ninth in ALEX, but he was next to last in conversion rate and dead-last in DVOA. The Packers missed the playoffs for the first time since the 2008 season.
Quarterback injuries were a major headline and sad development to 2017. Carson Wentz finished second in ALEX (+3.3) and conversion rate (49.2 percent), but he tore his ACL. On 28 third-down passes, Nick Foles disappointed with a 21.4 conversion rate and a +0.9 ALEX. Given Atlanta's defensive numbers we listed earlier, he might be in trouble this Saturday (and then against Minnesota next week should both teams advance.)
Deshaun Watson is not listed because he only had 43 attempts, but the exciting Houston rookie had +2.1 ALEX and a 41.9 conversion rate this year. You can see Tom Savage ranked seventh in ALEX in his place, and backup T.J. Yates had a +6.6 ALEX in limited action, but those aggressive passes were not nearly as successful as the ones attempted by Watson. We hope to see much more of him in 2018.
There's also going to be a ton of 2018 hype around Jimmy Garoppolo in San Francisco. He was only 16th in ALEX, but first in conversion rate at 52.8 percent. C.J. Beathard actually had some similar numbers to Garoppolo, his replacement, but he wasn't as successful. Brian Hoyer started the season for the 49ers but was far too conservative, as San Francisco kept losing close games until they got their big trade for Garoppolo.
Not everyone was badly injured this year. Ben Roethlisberger, Jameis Winston, Cam Newton, and Marcus Mariota all stayed healthy enough to have another high ranking in ALEX. However, Newton and Mariota were too erratic this season to have high conversion rates, with the lowest such rates of anyone in the top eight in ALEX. Newton had the largest ALEX pass of the season (+53) against Tampa Bay in Week 8 when he chucked a 57-yard bomb to Devin Funchess on third-and-4; it fell incomplete. The most successful high-ALEX pass this season was actually thrown by Atlanta wide receiver Mohamed Sanu on a trick play. Sanu threw a 51-yard touchdown bomb to Julio Jones on a third-and-1, which was also against Tampa Bay. That certainly adds some context to the numbers above on Tampa Bay's defense ranking last in ALEX.
The lowest-ALEX pass on third down this season was also very memorable. Against the Giants, Jared Goff threw a bubble screen a yard behind the line of scrimmage to Robert Woods, who somehow had blockers and a path for a 52-yard touchdown on third-and-33. That's a -34 ALEX, but it still went for a touchdown. We have nothing like that in the database. The previous low ALEX for a successful third-down conversion since 2006 was -27, done on some checkdowns by Eli Manning (to Ahmad Bradshaw in 2009) and Kyle Orton (to Garrett Wolfe in 2007). Goff and Case Keenum both ranked in the bottom eight in ALEX, but in the top seven in conversion rate. We'll have to see if they can continue that success in 2018, but both are definitely enjoying advantageous offensive situations (i.e., not playing for Jeff Fisher).
I keep getting tweets that accuse Tyrod Taylor of being a checkdown king, but he was 21st in ALEX and a solid 12th in conversion rate. Given the way the Bills let his receivers go to the Rams this year, I think those numbers are more than respectable.
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How about our usual Alex Smith check? He was right behind Taylor at 22nd (+0.7 ALEX), which is his highest finish since 2007. Smith was definitely more aggressive in his first 4,000-yard season, and he had a stellar first half in the playoffs last week. Unfortunately, it led to another second-half collapse, and Smith's biggest problem was really not pulling the trigger on some third downs. He tried to scramble and just couldn't make anything happen. (Patrick Mahomes only threw seven third-down passes in Week 17, but he had -0.6 ALEX if anyone's curious.)
In an article on a similar topic of aggression, Drew Brees was noted as running the most conservative passing game this season. His third-down ALEX was -0.2 (34th) and his conversion rate ranked 14th. That's notable in that his conversion rate had always been among the top eight in every season from 2006 to 2016. We'll see how Brees fares against arguably the best third-down defense of this era in Minnesota this week.
I like how the four quarterbacks after Brees are basically the scraps of the 2017 season. We talked about Hoyer before, but you also have the Dolphins dragging Jay Cutler out of retirement so he can throw 2-yard passes to Jarvis Landry on third-and-9. That totally did not work out. The Broncos got Brock Osweiler back and he was as terrible as expected. Then there's Mitchell Trubisky, the No. 2 pick in the draft by the Bears, who was lucky if he threw two passes in one drive at times. Similar to Goff in his rookie year, Trubisky did not have an easy situation around him, either with supporting cast or coaching. He also faced the longest third-down passing situations at 8.8 need yards, so that doesn't help with ALEX either. We'll hope to see more out of Trubisky next season with a new coach in Matt Nagy, who comes over from Kansas City.
Finally, ALEX is presented in splits by distance: short (1 or 2 yards to go), medium (3 to 6 yards) and long (7-plus yards). The colors indicate where a player is well above average (darker green) versus below average (darker red) based on standard deviations. Those conversion rates are also shown with a ranking.
It's obviously a small sample size, but it is reassuring to see Garoppolo finish with the highest conversion rate on third-and-short and third-and-long. Hoyer was dead last on third-and-long for the 49ers. Speaking of third-and-long, Keenum was 30th there as opposed to fifth in short and sixth in medium situations. He's not one for forcing things, so the Saints have a decent chance if they can win on the first two downs to bring up those situations on Sunday.
Random amusing fact: in Bruce Arians' swansong, Arizona was another offense that needed three quarterbacks (Carson Palmer, Drew Stanton, and Blaine Gabbert). All three ranked 31st or worse in third-and-medium conversion rate. Gabbert was dead last, which just goes to show that he can change teams and coaches as much as he wants, but can't change who he is.