Indianapolis has two defensive units.
One plays in Lucas Oil Stadium and has allowed 14.25 points a game and forced 11 turnovers in 4 games.
One plays on the road and has allowed 26.5 points a game and forced just 5 turnovers in 6 games.
The question is: why? Why are the Colts so much better at home than the road. Let's evaluate the popular theories:
1. Fast turf. This team plays faster on turf, or so they tell us. Specifically, the argument is that Freeney and Mathis play better on turf. Freeney has 5 sacks at home, and 2 on the road. Mathis, on the other hand, has 4.5 sacks on the road and 3 at home. That's a better rate overall in the Luke, where surely the crowd noise helps them. Over the past 3 seasons, Freeney has 13 road sacks and 18 at home. Mathis has 15.5 at home and 13 on the road. So Freeney specifically does look a like he's better at home than on the road. Freeney makes the defense go, for sure, and 8 Freeney/Mathis sacks in four games beats 7.5 in six games.
2. Schedule. The Colts played better offensive teams on the road than at home. By DVOA, the Colts have played the #1, 2, 3, 8, 15, 24th ranked offenses on the road. At home they've played #3, 10, 13, 21. That's a brutal road slate of offenses to face. There's a good chance that most of the point disparity is just due to playing the NFL's top three offenses on the road in six games. (note: DVOA stats don't include play this week...they will change today)
3. Offense's fault. The offense has started slowly and turned the ball over leading to points. By my count, the offense has had turnovers that turned into scoring drives in every road game but Denver. The offense has done the same in the Luke just twice (a garbage score against the Giants and a field goal for the Chiefs). By my count, the the offense has set the opponents up with 37 points off turnovers on the road (Including a Texans score on a long field after the Collie fumble week 1). 37 points in 6 games accounts for about half of the home/road point differential.
4. Falling behind-In the six road games, the offense has scored a total of 13 points in 6 first quarters. In the home games, they've put up 20 (plus 7 more on a Hayden pick six) in just four quarters. In addition, the offense has set up the opposition with short fields that produced 10 first quarter points on the road, and that hasn't happened at all at home. Falling behind means the opposition can run more, which compounds the Colts' problems.
5. Injuries-Gary Brackett has missed 2 road games and 1 home game. Clint Session also missed two road games and one at home. When you are talking about a very small sample size, being down two starting line backers for 1/3 of the total road games matters. Of course, both played and played poorly in a couple of the losses, so it's hard to know how big a factor this is.
6. Sample size-this could just be a fluke. Last year the D gave up 17.3 on the road and 18.1 at home (14 game totals...you know why). In 2008, it was 17.3 at home (not counting the Titans' end of season lay down) and 22.1 on the road. In 2007, it was 16.9 at home and 16 on the road. In 2006 it was 26.5 on the road (thanks to the 44 points by the Jags) and 18.5 at home. There doesn't seem to be a lot of consistency to this from year to year, which probably just means it's a whim of the schedule and in a small sample size, anything can happen.
No matter how you slice, Indy has four of their final six games at home. This week will be a stern test, but if the Colts' defense can rise to the occasion at home against the Chargers, the team will still have a very real shot at 11-12 wins and strong playoff seed.
From Aaron Schatz of the the Football Outsiders:
"I almost looked at the Colts home-road D thing this week for Numbers Crunch. But it is a fluke - it doesn't seem to exist in prior years. The home/road split is huge (in DVOA too). 2nd in DVOA at home, 27th on the road. They aren't the only team with a big split. Jets D 3rd home, 22nd road. Bal D 25th home, 2nd road (!)"