Adjusted Interceptions 2018
by Vincent Verhei
Patrick Mahomes, by most any reasonable measure, was the NFL's best quarterback in 2018. As such, he's a good candidate to decline in 2019, because when you start at the top, there's nowhere to go but down. Even beyond random fluctuation, though, there's reason to think Mahomes wasn't quite as good as his numbers looked last year, and that he's unlikely to get the same breaks this fall that he did back then.
Derek Carr, on the other hand, was a bad quarterback last year, but he too may have played worse than his numbers would indicate. The addition of Antonio Brown can only help, but that may be offset by a reversal of fortune.
Baker Mayfield, meanwhile, was a pleasant surprise, setting a rookie record with 27 touchdown passes in only 13 starts. Unlike Mahomes and Carr, Mayfield was a victim of back luck in 2018 -- and given that fate will likely smile more kindly on him this season, his future looks very bright indeed.
Welcome to the world of adjusted interceptions. Unlike the NFL's raw interception totals, these numbers account for plays when a defender drops a pass that he should have caught, or when a wide receiver makes a big play to turn what should have been a turnover into an incompletion instead. On the other hand, sometimes quarterbacks are charged with interceptions that aren't really their fault -- passes that bounce off a receiver's hands and straight to a defender -- or interceptions that don't matter, like Hail Mary passes.
After each season, we go back and account for these discrepancies and account for each quarterback's adjusted interceptions. Here's the process:
- We start with each player's actual interception total. Ben Roethlisberger led the NFL in 2018 with 16 interceptions.
- We then add plays where the quarterback threw a ball that could have or should have been intercepted but was not, either because the defender outright dropped the ball (which we have been tracking in game charting since 2007), or he had it knocked out of his hands by an offensive receiver (a "defensed interception," which we have been tracking since 2012). These are listed as "Drop/Def INT" in the table at the end of this page. Mahomes and Carr each benefited from a league-high ten such plays.
- Next, we subtract those interceptions that were tipped by receivers into the hands of defenders (as established in 2017, these plays can be thought of as Matt Ryan specials). Division rivals Andrew Luck and Blake Bortles led the league in this category with three apiece. We also subtract passes that are tipped by receivers but then dropped by defenders to make sure they are not double-counted. This only happened once last season, on a Luck pass.
- Finally, we subtract Hail Mary interceptions, as well as interceptions thrown in desperation on fourth down in the final two minutes of a game. We're flexible on these definitions -- this year, we included three interceptions thrown on fourth down while a quarterback was trailing in the final 2:30 of the game -- two by Sam Darnold against the Dolphins in Week 9 and one by Jared Goff against the Bears in Week 14. Counting that throw, Goff had three Hail Mary interceptions, most in the league. These are listed as "HM/End Q4" in the table.
When we started running these numbers, we had to get the data from our own in-house volunteer game charters. For the last four seasons, we've had access to data from Sports Info Solutions. Determining whether or not a defender should be charged with a dropped interception will always be subjective on some plays, but you can rest assured that all the obvious calls have been counted here.
Enough with the minutia -- let's get to the big table of numbers!
|Adjusted Interceptions 2018|
|Tip INT||Tip AND
|INT Rate||Adj Rate||Int
|Minimum 200 passes, plus Nick Foles because he almost made it and we wanted to include him.|
Our leaders in adjusted interceptions for last season were a pair of first-year starters. Mahomes and Darnold finish with 21 adjusted interceptions apiece. That's a pretty typical league-leading total; DeShone Kizer had 23 in 2017. Mahomes had 12 official interceptions. As mentioned, he benefitted from 10 dropped/defensed interceptions, while throwing one on a Hail Mary (on the last play of the first half in a Week 9 win over Cleveland). Darnold's numbers are similar. He had 15 official picks, one behind Roethlisberger for most in the league, while benefitting from nine dropped/defensed interceptions, also one fewer than the league leaders. However, we then subtract the two Hail Mary-esque interceptions discussed earlier, plus one more pick that was tipped by a receiver, to get to a total of 21.
There was a very tight cluster atop the adjusted interception leaderboards last year, with two players tied for the top spot and two more just one pick back. One of those players was Roethlisberger, who had five dropped/defensed picks on top of his 16 official interceptions, with one pick tipped by a receiver. The other is Carr, whose 10 dropped/defensed picks are added to his 10 official picks for a total of 20. Fifth-place Jameis Winston was just two picks behind the leaders with 19 adjusted interceptions -- 14 official, six dropped/defensed, and one Hail Mary (thrown while trailing by two touchdowns with nine seconds to go against Tampa Bay).
Looking at adjusted interception rates instead of totals moves a pair of Florida Men to the top of the tables. In only 273 pass attempts, Miami's Ryan Tannehill had nine official interceptions and seven more dropped/defensed, for a rate of 5.9 percent that was most among qualifying quarterbacks. The Dolphins got rid of Tannehill … and replaced him with the passer with the second-highest adjusted interception rate of 2018. Ryan Fitzpatrick threw 12 official interceptions with three more that were dropped/defensed, with one tip-drill interception. That's 14 adjusted interceptions in 246 passes, a rate of 5.7 percent. The lowest adjusted rate belongs to the player who also had the lowest raw rate. Aaron Rodgers only threw two interceptions last season, and even if you add in his six dropped/defensed picks, a total of eight in 595 passes (1.3 percent) is exceptional. He's followed by Drew Brees and Matt Ryan, whose numbers did in fact improve after a radically unlucky 2017 … which makes for a convenient segue to the topic of interceptions and luck.
On average, quarterbacks throw about 30 percent more adjusted interceptions than raw interceptions -- a player with 13 adjusted picks would be expected to finish with 10 actual interceptions. We can use that ratio to estimate how many interceptions a quarterback "should" have thrown based on his adjusted interceptions. Carr, for example, had 20 adjusted interceptions. Dividing that total by 1.3 results in a figure of 15.4. However, he only threw 10 official interceptions. That difference of 5.4 makes Carr the luckiest quarterback of 2018. He's followed by Mahomes (-4.2), Rodgers (-4.2), Tannehill (-3.3), and new Denver Broncos starter Joe Flacco (-2.5, in only nine starts).
At the other end of the spectrum we find Bortles. As mentioned, he led the NFL with three tip-drill interceptions last season, with only two that were dropped/defensed and one on a Hail Mary (this was one of those gray-area throws -- it came with the Jaguars at Kansas City's 14-yard line with nine seconds left and Jacksonville down 30-14). He had 11 actual interceptions but only nine adjusted interceptions -- the only qualifying passer with more actual than adjusted interceptions last year. That's 4.1 interceptions more than expected, making Bortles the league's most unlucky quarterback in 2018. He's followed by Mayfield (+3.2), Luck (+1.9), Case Keenum (+1.9), and Tom Brady (+1.8).
We can't guarantee that Carr, Mahomes, or Rodgers will throw more interceptions in 2019, or that Mayfield, Luck, or Brady will throw fewer, but history says that's likely to be the case. (Bortles and Keenum are the likely backups for Goff and Dwayne Haskins, so it's close to a lock their turnovers will drop.) Five quarterbacks threw at least one more interception than expected in 2017 and still started in 2018; all five of them (Cam Newton, Marcus Mariota, Deshaun Watson, Ryan, and Rodgers) saw their interception rates drop from one year to the next. Seven quarterbacks threw at least two fewer interceptions than expected in 2017 and started again in 2018; six of them (Philip Rivers, Alex Smith, Carson Wentz, Matthew Stafford, Brady, and Winston) saw their interception rates climb. Every quarterback goes through streaks of good luck and bad, but rarely do those streaks stretch into a second year.
Here's a look at adjusted interceptions in prior seasons.