Offseason Stat Crunch: Texas' 2006 Pass Defense
by Peter Bean on May 1, 2007 11:48 AM CDT
in Football
6 comments
The long, slow march through the offseason continues today with a statistical query inspired by Texas' dichotomous run-pass defensive splits in 2006.
Texas finished the 2006 season ranked third nationally in rush yards allowed per game (62.1). They also finished the season ranked 99th in pass yards allowed (236.2). In trying to wrap my mind around how big a difference that really is, I decided to dig through last year's stats to see how anomalous Texas' performance was.
Cick here for the rest of this story.
Take a look at the following chart, which lists the top 40 teams in rush yards allowed per game side by side with their pass yards allowed per game rank, as well as the delta. Teams with deltas greater than 60 are highlighted in yellow.
The data scatterplotted:
When I looked at these numbers, I immediately knew something was wrong. Take Michigan, for example, a team I watched frequently last season. Unable to run the ball even a little bit on the Wolverines, opposing offenses simply took to the air.
But what about the rest of the teams on the list? I suspected that this data was misleading, but I couldn't rule out the possibility that strong rush defense teams are simply more vulnerable to the pass. I decided to chart the top 40 ranked rushing teams by pass yards allowed per attempt
As suspected, the rankings for many of the teams improve dramatically. Michigan improves from 89th in total pass yards allowed to 20th in pass yards per attempt. Big improvements also for Florida, Penn State, UCLA, USC, Florida State, Ohio State, Oklahoma, Georgia Tech, Louisville, Wake Forest, SMU, Kansas, Boston College, BYU, Arkansas, Nebraska and New Mexico. Many more were ranked mildly better.
Only a few teams, though, were poor both in total pass yards allowed and in pass yards per attempt. And Texas was one of those teams. Even adjusting the data to control for the number of times opponents threw against the Longhorns, Texas still ranked 86th nationally.
Of the top 40 teams, only nine (West Virginia, Utah, SMU, Colorado, Washington State, Mississippi State, Navy, Arizona State, and New Mexico) joined Texas as below average (ranked 60th or worse) in pass yards allowed per attempt. Only three (West Virginia, Washington State, and Mississippi State) were outside the top 80. On a normal distribution, you'd expect six or seven teams to fall below that threshold, which suggests that these four teams were unsually inept at defending the pass in 2007.
Just looking at the numbers, we can't explain why Texas was so bad in pass defense; for that, we'd need to actually chart plays, re-watch the games, and scout mistakes. One thing's pretty clear, though: the Texas pass defense in 2007 - despite losing three starters in the secondary - can't be much worse statistically than the 2006 team.
--PB--
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Ugh
The scariest game of next season is starting to look like the other Oklahoma team, unless the new blood on the coaching staff can turn things around in a hurry. Who's gonna cover Bowman this year?
The best offense in the country is ...
With apologies to Florida and Louisville, it just might be Oklahoma State.
Call it a spring knee jerk, but to the naked eye, no team had more talent than Oklahoma State at the end of last season (No. 7 overall, 35.2 points per game). Give me quarterback Bobby Reid (29 total touchdowns), tailback Dantrell Savage (6.5 yards per carry), tight end Brandon Pettigrew and receiver Adarius Bowman and I'll take my chances.
by patienthornsfan on May 1, 2007 12:50 PM CDT reply actions 0 recs
brian cook, is that you?
i've always wanted a little more mgoblog on BON. good stuff.
with these stats, you can sort of see that, unlike a team like michigan, it wasn't a phenomenal run defense that was forcing teams to pass, it really was that teams knew they could be successful doing so. what might be helpful to flesh this out a little bit is looking at the same rankings for rushing defense. my guess would be that michigan is very highly ranked in terms of yards per rush allowed, while texas is good, but not great in that regard. if that were the case, it would be pretty obvious that it wasn't that the rush defense forced passes, but rather that the pass defense invited them.
however, there's a possibility that if you look at these stats, texas would be very highly ranked in terms of yards allowed per rush. if that's the case, it might get us closer to understanding why the dichotomy was so big. that is, texas was committing safeties to the run and/or linebackers were not blitzing the QB. so when runs occurred, texas stuffed them. but when passes were called, texas just didn't have the right scheme called -- linebackers weren't putting any pressure on the QB (giving him time) but had the middle of the field covered, while the safeties were looking into the backfield instead of helping out over the top, the combination of which is conducive to the deep pass.
by billyzane on May 1, 2007 12:56 PM CDT reply actions 0 recs
As it turns out
I was going to put a note about this in there, but got busy and wound up posting as is.
Anyway, the top 40 in total rushing yards are also, almost exactly, the top 40 in rush yards per attempt. I actually found that intuitive, as I'd guess that if a team was running the ball with any amount of success, they'd CONTINUE running the ball, rather than turn to the pass (even if they could).
Not surprisingly, then, Texas ranked 4th nationally in rush yards per attempt (2.35 per carry).
by Peter Bean on May 1, 2007 1:12 PM CDT up reply actions 0 recs
Sacks and blocked kicks
I don't there is a readily available dataset for this, but it would be more interesting if sacks and blocked kicks were counted as passing yards and special teams yards respectively. I don't know that it would make any huge differences, but we could see exactly what was happening on called pass and called run plays to get a more full picture of how the defense performed in those situations.
by Bob LaBlog on May 1, 2007 2:59 PM CDT up reply actions 0 recs
not sure i understand the point but....
it IS interesting that the correlation between rush defense and pass defense is so low (.17, not statistically significant from 0) - basically there's no relationship between rush and pass defense.
as you noted, the correlation between rush D and pass per attempt is higher (~.30).
by cortexas on May 1, 2007 3:20 PM CDT reply actions 0 recs
No eureka insights here
I was just curious whether any other outstanding rush-defense teams like Texas were equally inept at defending the pass.
Not many, it turns out.
by Peter Bean on May 1, 2007 3:21 PM CDT up reply actions 0 recs
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