Bama Basketball by the Numbers: the Defense

Like the Fremeau Efficiency Index for football, the Pomeroy ratings for basketball gauge the overall effectiveness of offenses, defenses, and teams overall as judged by their opponent-adjusted possession-by-possession efficiencies. Many college basketball blogs cite the Pomeroy ratings frequently, and I myself find them a quite effective tool for measuring the strength of a team and its component parts beyond just their win/loss numbers. According to the Pomeroy ratings system, Alabama has the 23rd strongest defense in the nation. Essentially, this is saying that we rank 23rd in opponents' scoring per possession when adjusting for the strength of the offenses we have faced thus far. Of the 22 teams considered to have stronger defenses, only one--Nebraska--is not currently projected as an NCAA tournament team.

To delve a bit further into the Tide defense from a statistical standpoint, we'll take a look at the "four factors". The idea here is that defensive efficiency in basketball is based on the following four key factors:

  • turnover percentage: how often do you force the opponent to turn the ball over before they have a chance to score? (turnovers per possession)
Alabama NCAA average NCAA rank
turnover percentage 22.6% 21.0% 94th

Bama forces turnovers on 22.6% of its opponents' possessions, above the national average and placing the Tide among the top third of the nation in forcing turnovers. These overall turnover numbers are good certainly, but not great--until you break them down further.

There are two types of turnovers: dead-ball and live-ball. Dead-ball turnovers are caused from either drawing offensive fouls or from the opponent committing a violation (traveling, stepping out of bounds, lane violation, etc). These types of turnovers are great because they give you defensive stops, but since the ball is taken out of bounds the defense has time to set up. The other type, live-ball turnovers, are caused by creating steals. These are even better than dead-ball turnovers because not only do you get a defensive stop, but they also create chances for instant offense in the form of fastbreak opportunities. It is here that the Bama defense under Anthony Grant truly excels. The Tide creates steals on 14.1% of opponents' possessions, which is good for 9th in the nation.

In sum, the Bama defense is good in creating turnovers overall, but great in creating live-ball turnovers that lead to transition opportunities on the other end.

  • effective field goal percentage: how well do you defend opponents so that their scoring is minimized when they do shoot? (shots made per shot attempt, adjusted for 3-pointers)
Alabama NCAA average NCAA rank
effective field goal percentage 40.8% 48.7% 6th

Bama is limiting opponents to only 40.8% effective field goal percentage, far below the national average of 48.7% and placing the Tide among the top 10 defenses in the country in this category. Bama is limiting opponents from both inside and outside the arc, but especially from inside.

Opponents are hitting 30.9% of their 3-point attempts, well below the national average of 34.2%, placing the Tide at 64th in the nation, or among the top 20%, in 3-point defense.

Inside the arc, however, is where the Bama defense is especially effective. Opponents are hitting only 38.2% of the shots inside the arc, compared to the national average of 47.5%, placing the Tide 3rd in the nation in defending inside the arc. This indicates that Bama has been especially good at preventing easy scoring opportunities around the basket, both in half-court sets and in transition.

One of the best ways to keep your effective FG percentage numbers low--and in Bama's case among the top 10 in the country--is blocking shots. The Tide is blocking a whopping 14.2% of opponents' shots, placing Bama 18th in the nation in that category--especially good numbers for a team lacking big-time size in the post.

Of the "four factors" effective FG% is the most important, since the majority of possessions do ultimately end in a shot attempt rather than free throws or turnovers. Here we are clearly one of the elite teams in the country, a major reasons we have a top-25 defense right now.

  • free throw attempt percentage: how often do you allow the opponent to get chances to score from the free throw line? (free throws allowed per shot attempt)
Alabama NCAA average NCAA rank
free throw attempt percentage 31.9% 37.8% 76th

This numbers really speak for themselves. The Bama defense is significantly below the national average in the rate at which it sends opponents to the free throw line, though by no means are we truly elite in this category. This is certainly a key component, though, as free throw discrepancy can be a huge factor in scoring. We've done quite well in this category defensively save four games: Seton Hall, Iowa, Purdue, and Providence. In each of those games we allowed far too many free throws, probably costing us the win in two or three cases.

In sum, this is an area we're not bad in aggregate but there's room for improvement.

  • defensive rebounding percentage: how often do you allow offensive rebounds that give the opponent further chances to score? (offensive rebounds allowed per shot attempt)
Alabama NCAA average NCAA rank
defensive rebounding percentage 32.7% 32.8% 169th

We are allowing offensive rebounds on 32.7% of our opponents' shots, which is virtually right at the national average. This is certainly not a strength of ours, but considering we are a bit thin in the post and we were missing our top post player for three games, it's not something that's a major weakness really either. This factor will become more important as we see more SEC opponents but suffice it to say, this is an area where we must continue to focus and improve if we want to maximize the effectiveness of our defense and therefore our ability to win games.

We'll take a look at the offensive numbers, which aren't quite as pretty, in the next piece.

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