Adherents to the old basketball saying, "offense wins games, but defense wins championships," must have been pretty excited about Texas basketball on the morning of Saturday, February 19. Texas had just completed locking down Oklahoma State, and had been playing soul-crushing defense on the rest of the Big 12 for the previous month. But later that day, the team suffered a loss at the hands of the Nebraska Cornhuskers. Losing a road game in February wasn't particularly surprising; the surprise was the way in which it happened. The Texas defense, not the often criticized offense, was responsible.
The importance of defense for the 2010-2011 Texas Longhorns.
Before I dig into discussing my take on what happened to the defense, I want to take a step back and emphasize just how important defense was to winning and losing for the 2010-2011 Texas Longhorns. So much of the talk around this team has been about offensive inconsistency, which misses the real story of the season. Prior to the Nebraska game, Texas had played consistently great defense, with a few occasional blips that usually led to losses. After the Nebraska game, Texas played poor defense in most of the remaining games.
On the season, when Texas played good defense, they won the game. When they played poor defense, they lost. Using the kenpom.com site, you can rank each Texas game by defensive efficiency. Of their 12 worst defensive showings, 8 were losses. Texas did not lose a single game when they played good defense. Contrast this with the list that ranks Texas games by offensive performance. There isn't nearly the same relationship between offensive performance and wins and losses for this team.
So if we want to understand the Texas season, we need to figure out what happened to the Texas defense. There are a variety of ways to measure defensive performance. Different measures incorporate different aspects of that performance. One that I find to be particularly informative is to look at the shooting efficiency of the opponent. As a shooting efficiency number, I like to use:
efficiency = points/(FGA+0.44xFTA)
This formula tells how many points a team or player scores for each attempted field goal or trip to the line. It is directly related to the so-called "true shooting percentage." (Note: I think that the 0.44 multiplier was determined by studying NBA games, and not NCAA games. There might be a better multiplier for the NCAA, but I don't know what it is, and I doubt it would be much different. If anyone could point me to this information, that would be appreciated.)
To help put this efficiency number into context, it is useful to calculate it for a number of the Texas players. Jordan Hamilton gets 1.11 points for every shot or trip to the line. Tristan Thompson gets 1.10. Generally 1.10 is quite good for an offense, and bad for the defense. Jai Lucas had 0.88 points for every shot or trip to the line this year, which is not so good.
We can evaluate the Texas defense with this statistic. It just shows us how efficient each shot or trip to the line was for the opposing teams. From the start of conference play on, we have:
Prior to the Nebraska game, Texas made many of its opponents the shooting equivalent of Jai Lucas. But in the losses to Nebraska, Colorado, Kansas State, Kansas, and Arizona, Texas' opponents were at least as efficient as Jordan Hamilton and Tristan Thompson. Even in most of the wins after February 19, opponents were still somewhat efficient. Baylor, OU, and A&M were much closer to Gary Johnson levels of efficiency (G.J. was at 1.04 on the season). In the games that Texas won, they held their opponents at or below the Gary Johnson efficiency level. In the games that Texas lost, their opponents shooting efficiency was as good or better than Jordan Hamilton's shooting efficiency.
What accounted for the changes in defensive performance as the season progressed?
I think we first need to understand what factors existed that made the Texas defense so good in the first place. For my purposes, I am just going to look at the Texas stats from the start of conference play through the NCAA tournament. I am doing this because I think it captures both the best and worst of the Texas season, as well as preventing games against teams like North Florida and the Naval Academy from skewing the numbers.
The Texas defense was exceptional at keeping opponent shooting percentages down. From the conference season on, opponents averaged just 29% from three point range, and just 45% from two point range. In addition, Texas didn't foul very much. Texas' opponents beginning with the start of conference play averaged 0.31 free throw attempts for every field goal attempt. Throw in the nice work Texas did all year on the defensive glass and you have a recipe for major success on defense.
We can dig a bit more into the numbers, using some of the handy data you can pull out of sportsline.com. They provide a breakdown of every shot taken in every game. They subdivide these shots into various categories, such as "layups" (really just shots taken near the basket), dunks, jump shots, 2 point shots, 3 point shots, etc. If we compile all of these data, we can find interesting things. For example, from the conference season on, Texas' opponents shot 29% from three point range, 33% on jump shots from two point range, and 31% on all jump shots. If we combine layups and dunks into a single category that I will call "shots near the rim," we find that Texas' opponents shot 56% on shots near the rim over this same time frame, and that 38% of all opponents' charted shot attempts were taken near the rim.
With these data, it is possible to study how opponents success rates with different types of shots changed from game to game. I have done this, and I think that the biggest factor, by far, was the opponents FG% on jump shots. There is a very strong relationship between opponent shooting efficiency and that opponent's FG% on jump shots. See the figure by following the link below.
The major factor in the Texas defensive collapse seems to be Texas' ability to defend jump shots. The Nebraska game seems to be the exception to this, as Nebraska only shot 35% on jump shots (Nebraska hurt Texas in other ways). But Colorado, Kansas State, and Kansas all averaged around 50% on jump shots. Arizona only hit 37% on their jump shots, but this number is a bit deceiving. Strangely, Arizona only managed 15% on 2 point jump shots, but hit 57% of their three point shots.
There are also a few other secondary factors that seem important. In the Texas losses Nebraska, Kansas, and Arizona were fairly effective at getting shots near the rim. Roughly 50% of all charted shots were near the rim in these three games. Texas also managed to put Nebraska and Colorado on the free throw line a fair amount.
Why did Texas stop effectively defending jump shots?
These statistics do a good job of telling us what happened, but they don't do much to explain why. I would be curious to know what people think.