For the last few seasons, the Houston Texans have continually threatened to make a run at the playoffs, but they haven't made it over the hump. There were always two problems. First, the Indianapolis Colts were in the way. And second, the defense was lousy.
This season, both those problems have been solved: the Peyton Manning-less Colts are terrible, and the Texans' defense is finally playing well. In fact, Houston's defense is playing so well that the team should be able to overcome the losses of starting quarterback Matt Schaub and backup quarterback Matt Leinart and make the postseason for the first time in franchise history.
The Texans actually rank No. 1 in the league in defense according to the official NFL standard of yards allowed per game. Now, the Texans' defense isn't quite that good. Houston happens to have played a particularly easy schedule of opposing offenses. But even if we use a metric which adjusts for opponent quality, it's clear that the Texans are much improved.
Football Outsiders' DVOA ratings take into account success on every play, comparing results to a league-wide baseline that is adjusted for situation and opponent (more explanation here). Last season, the Texans' defense ranked 31st in the NFL. This year, it ranks seventh. That's one of the biggest year-to-year improvements we've seen in the 20 years for which we have play-by-play breakdowns -- although, amazingly, Houston hasn't had the biggest defensive improvement in the league this season. (In fact, they haven't had the biggest defensive improvement in their division. That honor belongs to the Jacksonville Jaguars, who will be the subject of a separate article on ESPN Insider this weekend.)