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Median Age of Defensive Interceptions

Good instagram post by Tony Khan yesterday: Since 2001, there have been more interceptions made by defensive players aged 26 than by players of any other age.

That was true for this past season, too, where 70 of the interceptions came from players that were 26 years old in 2016. Perhaps more interesting: the median age for interceptions, by defenders, was 26 years. What do I mean by that?

Well, 2% of all interceptions in 2016 came from players 21 years of younger; 7% came from players 22 or younger, 14% from 23 years or younger, 28% from 24 or younger, 39% from age 25 or younger, and 56% from age 26 or younger. So if you sort all interceptions by the (ascending) age of the defender, you need to go up to age 26 to cross the 50% mark.

I looked at the September 1st age of every player who recorded an interception in each year from 1940 to 2015 (I haven’t updated by database for 2016 just yet). The graph below charts the median 9/1 age in each season (i.e., what is the youngest 9/1 age you need to use to make sure you capture at least 50% of all interceptions from player that age and younger): [click to continue…]


The Patriots won Super Bowl XLIX, and whatever your thoughts on the end of the game, there’s no doubt that New England was one of the top teams in the NFL in 2014. But it’s not quite so easy to identify why, at least when looking at the traditional per-play metrics. New England ranked 17th in Net Yards per Pass Attempt and 16th in Net Yards per Pass Attempt allowed, hardly the stuff of Super Bowl champions. The Patriots didn’t stand out as particularly excellent as a rushing offense or a rushing defense, either.

But those passing statistics belie the fact that the Patriots did, in fact, have a great offense this year. Part of the issue was the slow start and a meaningless week 17 game. Beginning in week 5, and excluding the week 17 game, New England scored 487 points, a 34.8 points per game average. That matches what the team did in 2012, when the Patriots had a historically lethal offense. And it’s not too far off from even the heights reached by the ’07 team.

The Patriots passing attack ranked 5th in TD rate, 3rd in INT rate, and 4th in sack rate; as a result, they jump from 17th to 6th when moving from NY/A to ANY/A. But the Patriots were even better at pure scoring.1 That’s been a trend for the team: during the Tom Brady era, New England has fared better in points scored than it has in ANY/A, and fared better in ANY/A than the team has in NY/A. And New England has generally been improving in all three statistics, too.

There is one area where the 2014 Patriots stand out as special. New England had just 13 turnovers all season: 9 Brady interceptions, three Brady fumbles, and one Brandon LaFell fumble. That is tied for the third best ever, although that sounds better than it is. The record for turnovers per game is 10 turnovers per 16 games, a feat accomplished by the 2010 Patriots and then the 2011 49ers. In 2014, the Packers also committed just 13 turnovers, and the Seahawks had just 14. As you might suspect, yes, this does mean that turnover rates have declined significantly in recent history. Take a look at the following graph, which depicts turnovers per 16 games for the average NFL team since 1970.  The purple line shows all turnovers; the blue and red lines are for interceptions and fumbles lost, respectively. [click to continue…]

  1. While New England moves at a fast pace, they actually ranked 3rd in points per drive and 4th in overall points, because the Broncos had even more drives than New England. []

Guest Post: Are Interceptions Overrated?

Guest contributor Adam Steele is back again. You can read all of Adam’s articles here.

Are Interceptions Overrated?

There’s nothing worse than throwing an interception. Everyone seems to agree on this, from fans to media to advanced stats guys. But is it really true? In this quick study, I looked at the tradeoff between interception avoidance and aggressive downfield passing to see which strategy has a larger impact on winning. To measure this, I created two categories of quarterbacks: Game Managers and Gunslingers.

First, the Game Managers, which includes all post-merger quarterback seasons with an INT%+ of at least 1101 and a NY/A+ of 90 or below (min 224 attempts).2 These guys avoided picks but failed to move the ball efficiently, the hallmark of a conservative playing style.

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  1. Which means the player was at least 0.67 standard deviations better than league average at avoiding interceptions. []
  2. Which means the player was at least 0.67 standard deviations worse than league average in net yards per attempt. []

Eli Manning in elite INT territory

After a five-interception performance against a dominant Seattle pass defense, Eli Manning now has 25 interceptions this season. The odds are extremely low, but it’s not impossible that he throws ten more interceptions and ties the modern record set by Vinny Testaverde in 1988. That year, a 25-year-old Testaverde threw 35 interceptions when the league average interception rate was 3.91%. Since Testaverde threw 466 passes that season, we could say that a league-average quarterback would have thrown 18.2 interceptions; therefore, Testaverde threw 16.8 interceptions over average that year.

So far in 2013, the average interception rate is just 2.70%. Since Manning has thrown 485 passes, we would expect a league-average passer to record 13.1 interceptions. With 25 interceptions, that puts Manning at 11.9 interceptions above average. The table below shows the top 100 leaders in interceptions over average since 1950. [click to continue…]


Analyzing every Joe Flacco interception this year

Flacco has had more downs than ups this year

Flacco has struggled to regain his Super form.

Over the course of his six-year career, Joe Flacco has generally done an excellent job at avoiding interceptions. Remember that quarterbacks are much more likely to be intercepted on deep passes, and Flacco tends to throw deep. Flacco has the 5th highest average length of pass this year according to NFLGSIS, after ranking 3rd in 2012, and 8th in 2011. But despite attempting more risky throws, Flacco posted better-than-average interception rates in each of his first five seasons. And he did that despite completion percentages that were often at or below league average.

Before the Super Bowl, I asked if Flacco was simply lucky to keep avoiding interceptions. That seemed like a good explanation for how an inaccurate passer who throws often downfield could have such a low interception rate. But other quarterbacks, like Donovan McNabb, sustained those traits for a long time.

This year, Flacco ranks in the top 7 in both interceptions and interception rate. So has lady luck simply switched allegiances? I looked at all 14 of Flacco’s interceptions this season to determine the cause.

1) Denver, 2nd quarter, 11:47 remaining, 3rd-and-9 from the Baltimore 16, trailing 7-0

Brandon Stokley is the primary receiver on the play. He’s lined up in the slot to Flacco’s left, and ends up running across the middle of the field at the first down marker. He’s in single coverage, but Flacco’s throw is a little short, and Chris Harris makes an outstanding play diving across for the interception. You can view the play here.
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On Tuesday, I look at the quarterbacks who have thrown the most pick sixes. As a follow-up, I wondered: what’s the record for pick sixes by a defensive player against a quarterback? Rod Woodson is the career leader in interception return scores with twelve, but only two of those came against the same quarerback (Steve McNair, thirteen years apart). As it turns out, there have been at least three defensive players who have scored interception returns against the same quarterback.

The first of three pick sixes.

The first of three pick sixes.

1) Ronde Barber vs. Donovan McNabb

Perhaps the most famous play of Barber’s career was his 92-yard pick six to clinch the 2002 NFC Championship Game in Philadelphia. The Eagles, trailing by 10, had driven down to the Tampa Bay 10-yard line with just under four minutes left in the game.  But Barber fooled McNabb into an easy interception, and raced down the right sideline for the game-clinching score. That was the second turnover of the day for Barber, who forced a McNabb fumble on a sack in the third quarter.

In 2006, Barber took back two McNabb passes for touchdowns in a defensive battle in Tampa Bay. The first pick six produced the only points in the first half, while the second gave the Bucs a 17-0 lead. But McNabb responded with three touchdowns, with the final one coming on a 52-yard reception by Brian Westbrook with less than a minute remaining. That gave the Eagles a 21-20 lead, which would have held…. except Matt Bryant hit a 62-yard field goal as time expired to give Tampa Bay the win. Philadelphia won the total yards battle 506-196, marking just the fourth time a team gained over 500 yards, allowed fewer than 200 yards, and still lost.

2) Bobby Bell vs. Charley Johnson
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Most Pick Sixes Thrown in NFL History

To pick six, or not to pick six

To pick six, or not to pick six.

Three years ago to the day, I crunched the numbers to see which quarterbacks had thrown the most pick sixes thrown in NFL history. With three more years of data, a robust play-by-play database, and, ya know, Matt Schaub, I figured it was time for an update. In case you haven’t noticed, Schaub became the first player to ever throw pick sixes (picks six?) in four straight games, and then on Sunday, T.J. Yates got the Texans into the record books as Houston had an interception returned for a touchdown in five straight games. But I thought it would be fun to look at the career leaders in pick sixes (and remind you that I discussed the rising rate of interception scores in the offseason).

Nobody has exact pick six data available, but we can do a reasonably job of answering the question of who has had the most passes returned for touchdowns in league history. That’s because we have:

  • Scoring logs for all scores, showing all interceptions returned for a touchdown, dating back to 1940
  • Play-by-play logs for all players dating back to 1999. So we have all the information we need from that point through week six of the 2013 season.
  • Individual game logs for all players, showing all interceptions thrown dating back to 1960.

For all pick sixes thrown since 1999, we have the precise data.  For any game from 1960 to 1998, we can do a very good job approximating who threw the pick-six. Most of the time, only one quarterback will throw an interception in any given team game. Fifty years from now, if you look at this box score from week six, you will be able to know for sure that Peyton Manning threw the interception that Paul Posluszny returned for a touchdown. The Broncos threw just one interception, and it was by Manning, so Manning must have thrown the pick-six. It doesn’t matter if the team has thrown five interceptions, as long as all were thrown by the same guy, such as Keith Null against the Titans in 2009.

The problem games are the ones where multiple players, usually quarterbacks, threw interceptions. For example, the record for defensive interception returns for touchdowns in a game is four, set by the Seattle Seahawks in 1984 against Kansas City. If you look at the boxscore, you’ll see that Todd Blackledge threw three interceptions, Bill Kenney threw two, and Sandy Osiecki added a sixth. So what do we do? Award Blackledge 2 pick sixes, Kenney 1.33, and Osiecky 0.67; obviously this isn’t perfect, but over the course of a player’s career, I think this will work well as an approximation. Because I’m running low on time, I’m going to just ignore pre-1960 data, although you could piece it together at the old link since obviously nothing has changed.

The table below includes all players who threw at least five pick sixes since 1960. It includes all postseason data, and unsurprisingly, Brett Favre is the career leader. He threw 10,960 career passes (including the playoffs), so he only threw a pick six on 0.32% of his passes (the leader in that category is Chris Redman, who threw a pick six once every 100 passes). Favre threw 366 career interceptions (again, including the playoffs), so he threw a pick six on “only” 9.6% of his interceptions. If you’re curious, Aaron Rodgers has thrown just one pick six in his entire career. That gives him a rate 0.032 pick sixes per pass attempt, the lowest among all passes with 1500 attempts since 1960.
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Throwing deep against Charles Tillman can be hazardous to your passer rating

Throwing deep against Charles Tillman can be hazardous to your passer rating.

Last off-season, I produced an exhaustive analysis of fumble recovery rates. With 13 years of play-by-play data at my disposal, I thought it would be worthwhile to take a closer look at interceptions. You can skip to the results section if you like, but let me start with a few disclaimers.

Interceptions are tricky to analyze. Interception rates are very inconsistent from year to year, so much so that completion percentage alone may be a better predictor of future interception rate than actual interception rate. But putting aside randomness, there are two other big factors that determine interception rates: the score in the game and the length of the throw.

Just about every quarterback will throw more interceptions when his team is trailing in the fourth quarter. Situation plays a huge role in football, and that’s true when it comes to interception rates, too. Similarly, quarterbacks are much more likely to be intercepted on deep passes than short ones. One thing I wanted to look at was how much league-wide interception rates varied over a wide range of circumstances.

Unfortunately, there still is a bit of bias in the data. The best quarterbacks are most likely to be winning and the worst quarterbacks are most likely to be losing. That means to the extent that trailing teams throw more interceptions than leading teams, the results are probably slightly overstated. Still, I think getting a sense of the league baseline over hundreds of thousands of throw — even if not evenly distributed — can be a useful exercise.

The Results

From 2000 to 2012, there were 6,689 interceptions thrown. Here’s the breakdown with respect to the points differential (i.e., points scored minus points allowed) for the offensive team immediately before the interception. For example, teams trailing by more than four touchdowns have thrown 110 interceptions over the last 13 regular seasons. That accounts for 1.6% of all interceptions thrown over that time period:
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On Thursday, I looked at the increase in pick sixes per interception in the NFL. Brian Fremeau asked if that was also going on at the college level, so let’s take a look.

In 2012, there were 159 pick sixes according to cfbstats.com, matching the number provided at Sports-Reference.com. That’s right in line with previous numbers. The table below shows the number of pass attempts, interceptions, and pick sixes in major college football games since 2006, courtesy of cfbstats.com.

YearPick 6INTAttINT RatePick 6 Rt

It’s pretty interesting that the interception rates in college and the NFL are nearly identical. The interception rate in the NFL was 3.1% in 2007 and 2.9% in 2011, just about what it was in college football in those years. And with the exception of the crazy-high Pick Six rate in the NFL in 2012, both leagues see about 10% of all interceptions returned for touchdowns. Unfortunately, I don’t have the data to see if the Pick 6 rate was 5% in the ’50s in college football like it was in the NFL. But my guess is the trend would hold and that there’s an inverse relationship between interception rate and pick six rate.


Good bit of trivia from my buddy Scott Kacsmar: there were 71 interceptions returned for touchdowns in 2012, the highest number in NFL history. Another interesting fact about the 2012 season: just 2.6 interceptions were thrown per 100 attempts, the lowest figure in NFL history.

We already know that the league-wide interception rate has been rapidly decreasing for years, but the significant increase in interceptions returned for touchdowns per interception is an under-reported story. Last year was the year of the Pick Six, but the Pick Six rate (INTs returned for touchdowns per interception) has been on the rise for several years. The graph below shows both the interception rate (100*INTs/Att) in blue (and measured against the left vertical axis) and the Pick Six rate (100*INT TDs/INT) in red (and measured against the right vertical axis):

Pick Six rate
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More work on POPIP and predicting INT rates

A couple of weeks ago, I wrote about interceptions per incompletion, or POPIP. In that article I showed how a player’s completion percentage is a better predictor of his future interception rate than his actual interception rate. And in this article by Brian Burke, one comment stuck with me:

Griffin has thrown deep, defined as attempts of greater than 15 yards through the air, on only 13% of his attempts, 30th among league quarterbacks. This is also likely the largest factor in his very low interception rate.

That makes sense — quarterbacks throwing short, safe passes should throw fewer interceptions. But this statement is a more important one than you might originally think, thanks to some great research by Mike Clay.

Clay came up with a metric he calls ‘aDOT’ — average depth of target — which measures exactly what you think it does. For each targeted or aimed pass, Pro Football Focus tracks how far from the line of scrimmage the intended target is. What’s makes this stat particularly appealing to me is that it’s very predictable as far as football statistics go. That’s not all that surprising because aDOT is based on a large sample of plays and basically frames how an offense operates.

Clay posted the 10 passers with the largest and smallest aDOT in 2011, which I’ve reproduced below. Note that there are some passes — spikes, throwaways, passes tipped at the line (these are grouped together as ‘other’) — with no target, and therefore are excluded when calculating aDOT. In the far right column, I’ve shown how the player’s aDOT compares to the league average rate of 8.8.

Tim Tebow20113182863213.3151%
Vince Young2011114111311.6131%
Jason Campbell20111651511410.5119%
Matt Moore20113473281910.4118%
Carson Palmer20113283121610.3117%
Eli Manning20117526985410.1114%
Cam Newton20115174942310113%
Joe Flacco2011605568379.8111%
Ben Roethlisberger2011553529249.8110%
Chad Henne2011112102109.7110%
T.J. Yates2011189171189.6109%
Matt Hasselbeck2011518490288.394%
Drew Brees2011763730338.293%
Blaine Gabbert2011413381328.192%
Alex Smith2011513463508.191%
Tony Romo2011522497258.191%
Ryan Fitzpatrick201156954425890%
Donovan McNabb2011156145117.989%
Colt McCoy2011463434297.888%
Tyler Palko201113512787.484%
Josh Freeman2011551519327.483%

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Interceptions per Incompletion (or POPIP)

The closest I'm willing to get with a baseball photo.

I leave the baseball analysis to my brothers at baseball-reference.com, but I know enough to be dangerous. There’s a stat called BABIP, which stands for Batting Average on Balls In Play. A “ball in play” is simply any at bat that doesn’t end in a home run or a strikeout. The thinking goes that luck and randomness is mostly responsible for the variance in BABIP allowed by pitchers to opposing batters. Pitchers can control the number of strikeouts they throw and control whether they allow home runs or not, but they can’t really control their BABIP.

Therefore, if a pitcher has a high BABIP, sort of like an NFL team with a lot of turnovers, he’s probably been unlucky. And good things may be coming around the corner. A high BABIP means a pitcher probably has an ERA higher than he “should” and that his ERA will go down in the future. In fact, you can easily recalculate a pitcher’s ERA by replacing the actual BABIP he has allowed with the league average BABIP. And that ERA will be a better predictor of future ERA than the actual ERA. At least, I think. Forgive me if my baseball analysis is not perfect.

Are you still awake? It’s Monday, and I’ve brought not only baseball into the equation, but obscure baseball statistics. Let’s get to the point of the post by starting with a hypothesis:

Assume that it is within a quarterback’s control as to whether he throws a completed pass on any given pass attempt. However, if he throws an incomplete pass, then he has no control over whether or not that pass is intercepted.
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