Training camp is around the corner and expectations for the Celtics this season are pretty high. That's mostly because the Celtics are returning almost everyone and reloading for a second run at a title.
But the band won’t be fully back together until, maybe, the calendar flips to 2025. Kristaps Porzingis’ rehab from a rare ankle injury seems to be going well, but even if it goes perfectly, he probably won’t return until Christmas.
Add to that the reduced offseason and added summer workload thanks to the Olympics, and we might not see full lineups at full minutes until after the All-Star break. And that's if everyone stays healthy between now and then.
The Celtics were the NBA’s second-best defensive team during last regular season and the third-best in the playoffs. Stopping opponents was a massive part of their incredible success, but with a few factors working against them, at least to start the season, it’s fair to wonder if they can replicate their incredible defense this upcoming season.
Starting without Porzingis is a major driver of this question. Porzingis’ rim protection was critical to the Celtics’ defensive success, and he was a big part of Boston’s best lineups.
According to Cleaning The Glass, Porzingis was tied with Derrick White for best defensive impact with opponents scoring 2.8 points per 100 possessions less when one of them was on the floor. The starting lineup of Porzingis, White, Jrue Holiday, Jayson Tatum, and Jaylen Brown had a 109.8 defensive rating in the regular season, lower than the team’s overall 110.6 defensive rating.
In fact, six of Boston’s top seven defensive rating lineups included Porzingis, including their best lineup which also included White, Brown, Al Horford, and Sam Hauser (though it was over 162 possessions as compared to the starters, who played 1,293).
Compare this to lineups with Horford instead of Porzingis. The starters with Horford had a 118.9 defensive rating last season, but they were still an overall plus because the offense was good enough to make them +1.3 overall. The Porzingis starting lineup, though, was +12.
So we enter the season with very clear evidence. The lineups with Porzingis were clearly Boston’s best, and his impact defensively was incredible. Horford certainly had his moments defensively, but there's simply no denying that teams shot better and scored more when he was in for Porzingis.
Now here we are a season later with Horford a year older. He’s been very reliable as part of a switching defense, but it’s also been clear that he’s not able to keep up quite as well as he has in the past. Also, Horford is very much at the stage of his career where he’s going to conserve some of his energy during the regular season so he has something left for the playoffs.
That's going to mean more blow-bys when a guard gets him on the perimeter. He’s not going to dog it defensively, but he’s not going to dig into those reserves to make some kind of remarkable chase-down play.
So what does that mean for Boston’s defense? Schematically, they’ll have to lean into his shortcomings and use more late-switching and rotations to try to make up the difference. After a year where Boston’s offensive fouls drawn rate dropped dramatically, we could see an uptick as they take a different approach to rim protection. White went from one of the most prolific charge-takers to almost eliminating it from his repertoire altogether. Without Porzingis to protect the rim and with Horford’s slower feet, he might have to slide in for a few in addition to trying to outright block shots.
It will add some pressure to the backups as well. Luke Kornet, in particular, could be plugged into the Porzingis defensive role because of his size. When I mentioned Porzingis being part of six of seven great defensive lineups, Kornet was part of the seventh. Interestingly, that lineup also featured Tatum, Holiday, Hauser, and Payton Pritchard. One might deduce that Kornet’s rim protection played a role in that. Neemias Queta’s size will come in handy as well, as will Xavier Tillman’s switchability.
Whether Boston can continue to defend at the highest level could simply depend on whether these guys can be effective until Porzingis gets fully healthy.
But it’s not just Boston’s bigs who have to step up. There will be a shared responsibility across the board. White and Holiday are going to have to match their defensive output from last season. Brown and Tatum are going to have to make statements as two-way players (which, to be fair, they kind of have already). Everyone is going to have to understand the balance between being aggressive defensively and not having a rim protector to bail them out.
That means we might see Boston give a little more pad between themselves and shooters to start the season. It could lead to some big 3-point nights for some players as Boston fears the drive and lives with the results. I’d imagine they’ll take the risk on hot shooting versus drives, fouls, and potential injuries as guys put their bodies in front of attackers.
It also means Boston will have to make up for some things on the other end. Joe Mazzulla always preaches the connectivity between offense and defense, so there is no doubt the Celtics will put an added emphasis on offensive execution as part of their defensive strategy.
To channel Mazzulla for a second, Boston will need to fight for their spacing to ensure driving lanes are open and shooters are in the right position for kickouts. There is added pressure to make the right decisions with the ball so they have the best chance at scoring and setting their defense. If Boston’s shooting percentages are good to start the season, a good enough defense will likely follow because they’ll get back and force lower percentage shots. The Celtics can’t mess around with their offense or else they’ll end up giving up a lot of points.
It might not matter in the long run if Porzingis returns when expected, ramps up effectively, and returns to his usual self. But if Boston’s defense struggles at all between now and then, it could impact their seeding, or worse, their habits. Spending months doing things one way carries a risk of guys reacting differently later in the season. Keeping their defensive discipline will be a challenge.
When it comes to the Celtics' defense, how they finish will be more important than how they start the season. But it’s fair to question how well they’ll be able to defend compared to last year and whether that will have a meaningful impact.