The Spurs defense is struggling and it could get worse

Without looking, do you think you’d be able to identify the most recent season during which the San Antonio Spurs finished with a defense that was worse than league average?

It was a really, really long time ago. Some of the people reading this post right now likely were not even born yet. Any guesses? No? Well, OK. It was the 1996-97 season, also known as the first year of Gregg Popovich’s tenure as head coach. The Spurs played the first 18 games of the regular season without star center David Robinson, then saw him get injured just two weeks later and remain out for the rest of the year. San Antonio finished the season with a 20-62 record and the NBA’s worst scoring defense per 100 possessions.

Of course, the Spurs also won the NBA lottery later that summer, drafted Tim Duncan, and proceeded to finish with a defense inside the top 10 every single season since then save for the lockout-shortened 2011-12 campaign, when they finished 11th. During Duncan’s career they finished first six times, second five times, third four times, and fifth once. It’s been two years since Duncan retired, and in those two seasons, the Spurs finished first and fourth in defense.

We’re barely a week and a half into the 2018-19 season, but if you fire up Basketball-Reference or the NBA.com stats engine or Cleaning the Glass and check the defensive efficiency standings, do you know where you’ll find the Spurs? Dead last. By a lot. Granted, it’s only four games into the season. But the Spurs between 1997 and this season had on average ranked 10th in defensive efficiency four games into the year. They ranked in the bottom half of the league only twice during that time.

During one of those two seasons, they actually did rank dead last after four games: in 2008-09, when their first three games of the year came against offenses that finished the season ranked second, first, and fifth in efficiency. That season, the Spurs still finished with the NBA’s fifth-best defense.

The Spurs often showed a similar ability to improve their defensive efficiency ranking after the first four games. In fact, only once from 1997 through 2018 did the Spurs have a better ranking after four games than they did at the end of the year. Between 1997 and 2018, they improved their defensive efficiency ranking by an average of 6.8 spots between their fourth game of the year and the end of the regular season.

Naturally, such a trend raises the question of whether this particular Spurs team can be counted on to continue it. In order to answer that question, it’s wise to dig deeper into the numbers. During the Duncan and Kawhi Leonard era, the Spurs always, always, always did two things at an elite level defensively: hold their opponents to low shooting percentages, and avoid fouling. They almost always cleaned the defensive glass at a high rate as well. Doing all three of those things made up for the fact that the Spurs never really forced all that many turnovers.

Consider the following chart, which shows where the Spurs ranked in each of the defensive Four Factors over the 21 seasons previous to this one.

As you can see, that’s consistently elite shot defense, consistently elite foul-avoidance, consistently near-elite defensive rebounding, and consistently sub-average turnover creation.

Peering into the Spurs’ defensive numbers this season, two things seem the same: San Antonio is once again not forcing many turnovers. Even in a year where the turnover rate is the lowest it’s ever been, the Spurs rank below-average in taking the ball away from the other team. Their opponents have turned the ball over on 12.1 percent of their possessions, which ranks 24th in the NBA heading into Thursday night’s play. Characteristically, the Spurs have avoided fouls. Through four games, they rank fifth in the NBA in opponent’s free-throw rate, sending them to the line only 0.217 times per field goal attempt.

Alas, because two things seem the same, that means two things seem different — the Spurs are, at this moment, having a below-average defensive rebounding season. Opponents have grabbed the offensive rebound off a miss 29 percent of the time, which means the Spurs have been the league’s 18th-best defensive rebounding team. The big change, though, is in their shot defense. Spurs opponents at this moment have a 57.2 effective field goal percentage, giving the Spurs the second-worst (or 29th-best) shot defense in the NBA thus far this season.

OK, so what does that mean? Surely, the field goal connection rate has to regress to the mean and the Spurs will once again resume their place in the league’s top 10 defenses. Right? Well, maybe not this time.

The percentage of Spurs’ opponents shots classified by NBA.com as “wide open” (meaning the closest defender was at least six feet away from the shooter at the time of release) has been steadily creeping upward for years, and it has crested to far this season at 26.5 percent — the fourth-worst rate in the NBA.

San Antonio’s opponents have an absurdly-high 66.1 effective field goal percentage on those looks and that number is almost certain to come down almost immediately, but it should be offset by the fact that San Antonio opponents are connecting at an unsustainably low rate on “open” shots, with the closest defender between four and six feet away from the shooter at the time of release. It doesn’t help that the Spurs are forcing “very tight” coverage on very few shots, with just 8.3 percent of their opponents’ attempts coming when the closest defender was within two feet of the shooter at the time of release. That figure ranks 28th in the NBA, when they had ranked first, first, 14th, 12th, and 24th in recent seasons.

This may all still scream REGRESSION to you, and perhaps it should. But also, perhaps it shouldn’t. Because the Spurs aren’t just giving up better-quality looks in terms of whether their opponent is open or guarded, but also in terms of the floor location of those shot attempts. The so-called “Moreyball rate” (the percentage of a team’s shots taken at the rim or behind the three-point line) has been steadily climbing league-wide for years now, but the Spurs had been able to largely stave off that rise. Not so much anymore.

According to Cleaning the Glass, 69 percent of non-garbage time shots against the Spurs have come from one of those two areas of the floor. That is by far their highest rate of the Cleaning the Glass era, which goes back to the 2003-04 season. The next-closest season was last year, when 63 percent of their opponents’ shots came from those areas.

And while, again, it may seem like the Spurs should be able to reverse that trend and get back to forcing inefficient shots, consider their personnel. For years they had either Tim Duncan, Kawhi Leonard, or both on their team. Even last year with Duncan retired and Leonard our for all but nine games, they had stalwart perimeter defenders in Dejounte Murray and Danny Green, plus limitless amounts of what Popovich calls “corporate knowledge” due to the fact that so many of their core players had played together for so long.

But now they no longer have Duncan. They no longer have Leonard. They no longer have Green. Murray is out for the season. Their best defender is likely LaMarcus Aldridge, and while he is underrated on that end, he is not a “top 10 defense unto himself” type of defender. They have guys like Patty Mills and Bryn Forbes and Rudy Gay and Pau Gasol and DeMar DeRozan and Marco Belinelli playing heavy minutes.

They do not have a prototypical stopper on the wing or at the point of attack. They do not have a do-everything big man who can plug all the leaks. Their players do not have years of experience defending every situation and the ability to communicate everything with just a quick glance. This is largely a group of guys that have never played together before. (Mills, who has been with the team since the tail end of the 2011-12 campaign, is now the longest-tenured Spur.)

They can be pierced from the perimeter and they are not especially well-versed in rotating on a string just yet. They have not been very good at matching up in transition. They have not been forcing the right kinds of shots nor have they been contesting the ones they do force at a very high rate. There does not seem to be all that much hope for improvement down the line, considering the personnel. You’re basically just banking on Pop being able to magic up a defense. He’s done it before, but he’s also had far better infrastructure and players with far more experience playing for him. He no longer has either of those things. And so perhaps this really is the year the Spurs defense finally falls off the map.