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Examining the Spurs’ mediocre defense

San Antonio currently ranks 20th in defensive rating. Here are some numbers and takeaways around an area that was expected to be a core strength the season.

LA Clippers v San Antonio Spurs Photos by Michael Gonzales/NBAE via Getty Images

The Spurs were expected to hang their hats on the defensive end of the floor this year, the product of shifting away from offensively inclined vets like DeMar DeRozan and LaMarcus Aldridge and fully leaning into a youth movement built around switchable perimeter players and a prototypical drop big coming into his prime.

Statistically, at least, that hasn’t happened. Past the season’s halfway point, San Antonio owns the 20th ranked defense, which has fared a tick worse than its 17th ranked offense. Lineups have varied greatly night to night this season, but it’s still worth looking at these numbers in the aggregate and trying to see where things are breaking down. Here are some stats and takeaways.

110.0 - Spurs’ defensive rating (20th in NBA)

The defense hasn’t held up as well as expected in the aggregate thus far, allowing 110 points per 100 possessions. That’s actually better than last year’s mark of 112, which ranked 17th, but scoring in the NBA has taken a major dip due to a variety of factors, and so expectations adjust accordingly. While a game or two can swing this figure — after all, Brooklyn’s 14th ranked defense allows just 1 point per 100 less than San Antonio’s — top-10 Minnesota is at 108, which speaks a bit more to the space between where we thought the Spurs might be and how they’ve performed.

107.4 - Defensive rating of Spurs’ preferred starting five

That number improves when the Spurs’ ideal starting group of Murray, White, Johnson, McDermott and Poeltl play — and when all five guys are not injured or battling Covid. They own a 3.4 positive net rating that skews towards defense, allowing 107.4 points per 100 possessions, which would put them just behind the 6th ranked Celtics defense of 107.0.

97.6 - Spurs’ defensive rating in clutch time (5th in NBA)

This remains a small sample size (75 total minutes), but it’s worth nothing the Spurs’ defense has not been the reason behind their poor end-game outcomes. That would be the offense, which ranks dead last (89.4 offensive rating) in close games.

111.7 - Doug McDermott’s defensive rating (worst among SA rotation players)

106.6 - Derrick White’s defensive rating (best among SA rotation players)

Technically, Jock Landale’s 104.5 bests White’s number here, but his numbers don’t pass my arbitrary threshold yet. Analytics heads will often tell you defensive rating is not an individual stat, but it’s still worth looking at players that share minutes and have an idea of where the numbers have tugged or jumped.

55.9 - Shots contested per game (2nd in NBA)

In a vacuum there’s not a qualitative point to make with this stat, but it at least shows the Spurs are active and contesting shots at a high rate. Furthermore, no team has defended more “tightly contested” shots (within 2 feet) than the Spurs at 8.9 per game.

Now, there’s a flipside to that stat, so here are two more numbers for you.

29.3 - Opponent FGAs per game in restricted area (2nd highest in NBA)

61.6% - Opponent FG% in restricted area (Tied - 3rd lowest in NBA)

So, the Spurs are contesting plenty of shots (good) but they are happening at the rim (bad) and teams are shooting well below average from there but at an objectively good clip nonetheless (also bad, still over 1.2 points per attempt). That doesn’t give a full picture, but it you at least get an idea of an opponent’ shot diet. Here are a few more.

33.6 - Opponents 3PAs per 100 possessions (7th lowest in NBA)

35.5% - Overall opponent 3 point percentage (10th highest in NBA)

40.8% - Opponent 3 point percentage on wide open threes (Highest in NBA)

The Spurs allow roughly two fewer three-point attempts than league average per game; teams are making those at a higher clip, however, and especially when left wide open. Those wide open looks make up almost half of the total number of looks the defense gives up, so the Spurs’ bad fortune in how well those open shooters are making them starts to add up.

All of this is connected. Players may get wide open because the Spurs are hedging, helping, or breaking down elsewhere in possessions that may have otherwise led to a look at the rim. This seemed to especially be true at the start of the year as off-ball defenders over-helped at the nail and gave up clean looks from distance. The eye test may hint at some issues with containing the pick and roll or teams hunting, say, McDermott on switches but, in the end, we’re still trying to connect a handful of moving dots.

45.1% - Opponent FG% on midrange attempts (highest in NBA)

When the Spurs aren’t getting burned on open threes or around the rim, teams have been white-hot from the spot on the floor San Antonio once buttered its bread. Given that the Spurs almost always have a traditional non-switching 5 on the floor and play drop pick-and-roll coverage, it makes sense that opponents would scheme accordingly and hunt those looks.

45.1% is a percentage point higher than 2nd most and 4 or 5 percentage points over league average — not a big difference, but losing on the margins can add up, especially when you’re not an offensive juggernaut.

14.6 - Deflections per game (11th in NBA)

14th - League rank in steal rate

10th - League rank in block rate

Deflections is a stat where the Spurs started out hotter and has come down, while Murray continues to rank among the league’s most prolific with 4.7 a game. It’s a fine category to rank high in but not required for a good or great defense, as shown by some of the teams that feature in the top 10. Overall the Spurs make plays on defense, but maybe not quite at the clip we expected. It’s worth wondering how that might look with more size on the wing complementing Murray, White and Poeltl.

71.5% - Defensive rebound rate (22nd in NBA)

14.7 - Opponent second-chance points per game (27th in NBA)

The Spurs rank in the bottom third of offensive rebounds allowed, and teams have made them pay for it. While Jakob Poeltl has been a workhorse for them on both ends, San Antonio plays almost exclusively small at the 3 and 4, and a long-term question for this team is what kind of players they envision at those spots, whether that’s with Poeltl or not. It’s worth noting that Johnson, who’s often been the de facto small-ball 4, has solid rebounding numbers on an individual and lineup-based level, while defensive rebounding rates have taken a hit with lineups that include Devin Vassell or Lonnie Walker, both of whom also shift up a position regularly.

11 - Opponents fast break points per game (4th in NBA)

While San Antonio’s size doesn’t play into its favor on the glass, it does in transition defense, where they limit opponents’ chances at getting on the break and are among the best on a per-possession basis of stopping them from scoring.

Takeaways

In general there’s not one particular player, lineup or reason to point to why the Spurs have underwhelmed on the defensive end thus far. The front office made a concerted effort to instill a new identity and style and these results aren’t a knock on that. Looking under the hood does give us a few factors to unpack, however: namely, health, lack of size, and luck.

The latter is out of the Spurs’ hands, especially in a pandemic, but a lack of experience, depth, and continuity behind the starting five quickly compounds the problem when one or more players go down. The lack of size hurts them on the boards and likely in the paint overall, and they continue to be on the wrong side of fortune when it comes to the open looks opponents have hit. As none of those three factors are entirely within the team’s imminent control, it becomes hard to project a turnaround, although a collective regression to the mean would probably help.