Are the Spurs trading transition defense for offensive rebounds?

NBA.com’s John Schuhmann pointed out an interesting statistic the other day regarding the Spurs 1st half and 2nd half offensive splits. It turns out that the Spurs, who hold the league’s 3rd most efficient offense overall, are much more efficient on offense in the 2nd half than they are in the 1st half.

Similarly, the Spurs have been historically great on defense all season long and hold one of the lowest Defensive Ratings[1. Points allowed per 100 possessions.] in league history. However, their DRTG in the 1st half of games is significantly better than it is in the 2nd half.

There are probably a large number of factors that play into this trend. The most obvious being that the Spurs play their bench players significant minutes and it’s possible that the closing unit is more well-rested in the 2nd half than their opponents. The Spurs have also been ahead by a wide margin entering 4th quarters and it’s possible that garbage time skews some of their advanced statistics.

However, there are some interesting trends in their regular season data that point toward a deliberate change in emphasis between the first half and second half that are worth exploring. Most notably, their approach to offensive rebounds and transition defense.

Offensive rebounding vs. Transition defense

As has been argued on this site before, there is often a trade-off between offensive rebounds and transition defense. Teams that pursue offensive rebounds aggressively, especially from the guard and wing positions, tend to allow more points and field goal attempts in transition than teams that do not pursue offensive rebounds quite as hard.

The logic for this is fairly basic. Guards and wings are usually the deepest guys back at the time of any given shot attempt. They are also charged with stopping the ball in transition. The quicker that an opponent is able to get the ball up the court, the harder it is for the defense to match up in transition and prevent an open shot attempt. If teams over-pursue the offensive glass with their wings, there are usually fewer guys back to stop the fast break and match-up in transition.

However, almost all teams play at a slower pace in the 2nd half. Only the Utah Jazz played faster in the 2nd half this season. On average, the pace in the 2nd half was 2.18 possessions slower  than it was in the 1st half over the course of the 2015/16 season. Teams on average also produce fewer fast break points in the 2nd half by about 0.5 points per half. Both of those numbers seem marginal but it might be enough to tilt the OREB/transition defense trade-off in the favor of offensive rebounding.

In the 1st half, the Spurs ranked 24th in OREB%, grabbing just 21.1% of available offensive rebounds. In the 2nd half, the Spurs grabbed 25.2% of available offensive rebounds, good for 8th best in the league.  The 4.1% leap from the 1st half to the 2nd half is the largest leap a team made between halves in the league.

Similarly, the Spurs allowed 1.2 more fast break points in the 2nd half than they did in the 1st half and were one of just seven teams to allow more fast break points in the 2nd half as opposed to the 1st.

A 4.1% increase in OREB% might not be enough to make a big enough leap in offensive rating to counteract the extra transition play allowed, but it does point toward a possible trend in how the Spurs approach the risk-reward balance on offense. It could just be that the Spurs place a much larger emphasis on sending two or three guys back on defense after a shot goes up to prevent easy transition opportunities in the first half while in the 2nd half they place a larger emphasis on being aggressive on offense. Not only does this mean chasing offensive rebounds but also possibly trading floor balance for spacing.

In order for a team to be sure that they are getting multiple guys back in transition, they often have rules that state at least one or two guys must be above the break at all times in case there is a turnover or quick shot attempt and rebound. If a team is willing to be more aggressive, they will send more players deeper down the court, either remaining in the corners longer or by attacking the paint off of drives and cuts.

It’s all speculative based on the surprising trends in the data but it looks like Spurs are deliberately zigging because they know that the entire league tends to zag in the 2nd half. As Schuhmann mentions in his tweet, the 1st half defense, 2nd half offense trend has continued in the playoffs. As with everything the Spurs do, I wouldn’t be surprised if the rest of the league follows suit very soon.