Writers of Pro Football Prospectus 2008

19 Mar 2007

June Bugged

Here at FOX, he's called the "Tackle Machine." At the four-letter network, they called him a "Standout Linebacker." He's Cato June, the former Colts weakside linebacker who just signed with the Buccaneers. Tackles are his calling card: he registered 142 of them this year, his third straight season with more than one hundred. Surely a player who brings down almost 10 opposing ball carriers per game represents a significant upgrade for the Bucs defense, right?

Well, maybe.

Tackle statistics are among the most misunderstood numbers in football. They aren't even "official" stats, but they are easy enough to find on various websites, so fans and writers freely bandy them about. When we see that Zach Thomas made 165 total tackles (103 solos and 62 assists), we assume that he's doing a heck of a job. And we are usually right: it takes a pretty good defender to top 100 tackles. But there's a big problem: tackle totals are highly distorted, and the distortion favors players on bad defenses. That means that the players on top of the tackle leader boards aren’t always the best defenders in the league. Instead, they are often the best players on lousy defenses.

Imagine a defense so good that it always causes opponents to go three-and-out. Such a defense would only record one or two tackles on a typical series: two tackles and an incomplete pass on third down. If that team's offense was competent, then opponents would be throwing the ball to catch up in the second half, creating more incomplete passes and fewer tackles. That's why great defenses often record low tackle totals. The 2006 Ravens recorded just 826 total tackles, the fourth-lowest total in the league. The Bears were also below the league average.

Now flip the scenario and imagine a defense that allows a lot of long drives. Every 80-yard drive represents eight or nine tackles for the defense, even though the unit isn't doing a very good job. The tackle total increases if the run defense is bad, because running plays produce more tackles than passing plays. It goes up again if the team is good at avoiding big pass plays: one 50-yard bomb results in one tackle, but 10 five-yard runs often yield 10 tackles.

A team with a bad run defense that's great at avoiding big pass plays? Wait, I just described the Colts! The Colts defense recorded 1,010 total tackles, the fourth highest total in the league. Here's a list of the teams that recorded over 1,000 tackles last season, along with their DVOA rank in run defense. Notice the trend:

Team Tackles Run Defense Rank
Bills 1,076 29th
Titans 1,059 28th
Jets 1,052 32nd
Colts 1,010 31st
Bucs 1,004 9th

It's pretty clear that high tackle totals are partially the result of an inept defense (the Bucs crash the party because their terrible offense kept the defense on the field forever). The Colts registered nine percent more tackles than the league average. For June, nine percent amounts to about 13 tackles.

But that's not the only distortion affecting June's stats. June's 96 solo tackles ranked 10th in the NFL among linebackers, but his 45 assists ranked fifth. Assist totals can be a little funky. Last year, the average team recorded 701 solo tackles with a standard deviation of 42 (I'm rounding to whole numbers because that's what I do). To de-mathify a little, that means that most teams register between 659 and 743 solo tackles, not much of a spread. The mean for assists was 226, but the standard deviation was a whopping 60, which means that "average" assist totals spread all the way from 166 to 286. With 257 assists, the Colts defense was in the high average range.

If you hate math, you can start reading again. The point is that there may be some disparity between what scorers in different cities call an "assist." In St. Louis (just 85 assists), a defender might have to have his arms around the runner's knees while the main tackler wraps his chest. In Buffalo (352 assists), a defender just has to chest-thump the main tackler after the play to earn an assist. We discovered two years ago at Football Outsiders that some scorers are very generous when doling out "passes defensed" to defenders in cities like Philadelphia. We haven't studied this issue in detail, but the phantom assists were a big problem in the days when teams kept their own tackle data, which is why you can't rely on the totals you see in team media guides from before about 1994.

So June's high assist total may be the result of some extra generosity on the part of the local scorers. Meanwhile, he picked up an extra 13 tackles from playing on a bad defense. Total it up, and his 142 tackles may equate to about 120 for an average defense. That's still a lot of tackles, but it isn't an unusual number. Dozens of linebackers finished with over 100 tackles; most of them are good players, but all of the distortions in the data make it impossible to say that the 120-tackle defenders were better than the 100-tackle players. And the sheer number of guys like Morlon Greenwood and Chris Draft who cracked 100 reminds us that 100 tackles isn't much of a milestone; most teams have one or two linebackers and safeties who approach the century mark every year.

Now, I spent weeks breaking down tape of the Colts defense in December and January. I saw the good and the bad, and I saw a lot of June. He's a very good coverage linebacker. He's a below average run defender. I also have a spreadsheet full of Football Outsiders breakdowns: how many tackles he made on passing plays, how many on rushing plays, how many near the line of scrimmage, how many down the field, and so on. The breakdowns have their own distortions, so I won't go through them all here. But they back up my scouting notion that June is at his best in coverage and makes too many of his tackles after significant gains. June's average tackle occurred 5.3 yards downfield, a poor figure for a linebacker, though its true that he made many tackles after long gains because he was cleaning up his teammates mistakes.

The Bucs signed a good linebacker. June fits their system, and he makes their greybeard defense younger. He'll help the pass defense. But let's 86 the "tackle machine" rhetoric. June made a lot of tackles because there were a lot of tackles to make. Ironically, if he really makes the Bucs defense better, then his totals will go down.

Posted by: Mike Tanier on 19 Mar 2007