The Spurs's five-subs lineup of Neal-Ginobili-Jackson-Bonner-Splitter was one of the most used last season and boasted a stellar 13.5 net rating, mostly due to an explosive offense. This season it's very rare to see a five subs lineup, partly because of injuries but more likely because they just don't work. The most used bench lineup including Ginobili this season (Blair-Diaw-Jackson-Ginobili-Neal) has been atrocious on offense, scoring only 80.4 points per 100 possessions, resulting in a -8.4 net rating.
Last year's bench would often hold or extend leads, and that doesn't seem to be the case this season. Some individual players are underwhelming on offense (as the almost 10 points drop-off in combined points per game for the five most used subs show) but it seems that the bench as a whole is struggling. Let's look at the reason why and then I'll tell you why I'm not worried about it.
Tiago Splitter is now starting
Splitter was stellar last season. He rebounded well, finished at a high rate and anchored a second unit that, while not great on defense, held its own. The inside presence he provided on both ends of the floor is sorely missed now that Boris Diaw and DeJuan Blair have taken his place.
Diaw is a good player but he isn't a natural big. He definitely has his talents, but Boris is a terrible rebounder for the position, a bad screener and a bad finisher. He is not a threat on a pick and roll and his reluctance to shoot makes him a bad pick and pop player.
Blair keeps the tradition alive by being featured in lineups that do terribly with him on the court and much better when he is replaced. The Neal-Ginobili-Jackson-Diaw lineup with Splitter in Blair's place sees a ridiculous 55.1 turnaround in net rating, mostly due to much better offense. Sample size is a problem with most lineup data but this has been a constant on Blair's career.
Stephen Jackson has been awful
Since returning to the Spurs, Jackson has been consistently terrible in the regular season. At this point in his career and with the role he has, Jack seems to be biding his time until the playoffs start and at least last season he could revert things and become a valuable contributor for the team. But in the regular season his subpar (and that's being generous) outside shooting, turnover proneness and at times disinterested defense hurts the bench's productivity. It's all about the playoffs with Jack and he has suffered injuries but his play has been undeniably awful.
No fourth big or secondary playmaker has emerged
Bonner and Blair have been very inconsistent and they don't really fit well next to Boris at all. Bonner is supposed to provide better positional defense and floor spacing and Blair rebounding and a diving threat on the pick and roll but neither has been able to do it consistently.
Similar to the situation with the bigs, the Spurs have a lot of point guards and combo guards that are limited but competent. Unfortunately, none of them has displayed their abilities and masked their weaknesses consistently enough to earn that spot next to Manu Ginobili as the bench's secondary playmaker. All back up guards, like all back up bigs, struggle mightily on defense. They also all lack something on offense, be it shooting or playmaking. Cory Joseph is perhaps the most well-rounded of them all but up until a couple of weeks ago he seemed a lock to be out of the playoff roster and hasn't had a lot of reps with the bench guys.
The current bench is not a good fit for the new system or the old one
While the bad defense of the second unit is easily explained by noting that most of the bench players are not particularly good defenders and that there is no one that can protect the rim, the offensive problems seem a little harder to explain. In reality the answer is simple: the personnel is not adequate to either run the spread pick and roll sets the Spurs used a lot last season or the off ball motion offense the Spurs are using more this year.
A lot of the plays the Spurs run offer two options, one inside and one outside. With no real inside scorers and only one credible outside threat in Gary Neal/Ginobili, reading the plays is easy for the opponent. Ginobili is a good of ball cutter but the rest of the bench isn't. The back up bigs either can't shoot the mid range jumper (Bonner and Blair) or are reluctant to pull the trigger (Diaw), so running a side pick and roll as a decoy to allow the other big to step outside and hit a free throw line jumper is not an option.
So if the Spurs run a pick and roll with Manu and Blair and with Jackson and Diaw on the court spacing the floor, teams will immediately cheat off Diaw and pinch off Jackson to make the catch after diving harder. If the ball is instead swung to the open man, who will almost definitely be Diaw, he probably won't take the shot. With the paint packed and no great outside options the ball handler has very little choice other than force a drive or settle for a long jumper, which helps explain why sometimes it feels Ginobili and to some extent Neal are forcing things.
If instead of high pick and rolls the Spurs run a lot of motion off the ball, the screens are usually not good enough to get the defense out of place and the scoring threats, both in the post and in catch and shoot situations, are either non existent or not particularly scary. That only leaves the option to run simple things, like getting Neal curling off a screen or a 1-3 side pick and roll with Jackson, to attempt to force the switch and get him in place to post up a smaller defender. You can only run that a couple of times before the opponent makes the read and adjusts.
So all is lost and we should panic?
No, not really. By removing Splitter from the bench unit and fading out guys that he doesn't trust like Blair, Bonner, Mills and De Colo, Pop has made it clear that his focus is on the postseason. I sincerely doubt that the Spurs will sit both Duncan and Splitter at the same time in the playoffs, at least for long stretches, so there will always be an inside presence. Jackson has a tendency to play better in the playoffs and even if he doesn't Leonard is showing that he can play well in heavy minutes. Similarly, Parker will probably get a lot of minutes in the playoffs so who backs him up won't be that big of a problem.
A nine man rotation of the starters plus Neal/Joseph, Ginobili, Jackson and Diaw in which the bench players are mixed and matched instead of having all subs lineups should provide the team with much more balanced units that allow them to run both the new variations of the offense as well as the always effective pick and roll. On defense, better effort from Jackson and Ginobili, having Parker on the court and one of the two good interior defenders in for most of the game will definitely solve a lot of the defensive problems we are seeing now.
Stats courtesy of NBA.com/Stats
If you found this article interesting, you should definitely check out these two fanposts: Seven games after Tony Parker and Statistical excursions: Life without Tony edition.