The Celtics' biggest issue when they weren't playing their best basketball was their defense. It was, at times, lazy or even non-existent. but that has changed recently, and not surprisingly, so has their record. They are rolling, and they're doing so behind a more engaged defense. Three of their four lowest point totals allowed have come in 2025. Their overall defensive rating is 109.6, fifth in the NBA, but their February defensive rating is a tick below that (109.3), which, if it holds, would be their second-best defensive month of the season so far (106.4 in December).
The Celtics are a uniquely built team that simply has advantages everywhere on the floor. They can play different ways on defense, which allows them to confuse opponents from possession to possession. They also have guys who do things they probably shouldn't be able to do, and that lets the Celtics get funky, especially when opponents throw non-shooters into the mix.
We saw that against New York, with Boston laying way off Josh Hart every possession in order to pack the paint and protect the rim. Here's how it looked:
Kristaps Porzingis starts out on Hart and when Hart goes to set a pick for Jalen Brunson, Porzingis sags way off him, allowing Jrue Holiday to navigate his way under the screen and get out to Brunson's shooting hand quickly. Porzings then helps way off Hart on the drive, forcing Brunson into a fadeaway jumper rather than an attempt at the rim. Not only is it a tougher shot, there's very little risk of a foul.
Brunson didn't shoot a free throw against Boston on Sunday. He shot 13 against them the last time they played.
Porzingis dropping way off Hart allows Boston to navigate his screens better. There is plenty of room for them to dip under and around him.
And knowing that Porzingis is always going to be back in the paint allows the Celtics to take aggressive chances.
Jayson Tatum was not worried about losing his man because he knew the paint was protected. Tatum may not make that play against a team full of shooters because Porzings would have been more worried about his guy on the perimeter instead of reacting to the cut and making the steal.
The Celtics are able to employ this strategy because they have other defenders who can handle what would normally be Porzingis' assignment. In those three clips, Tatum is defending Karl-Anthony Towns twice and Al Horford once. And as we've seen before, Jrue Holiday has his turns on the opposing big, too.
In these clips alone we've seen Holiday cover Brunson and Towns, an important element to the Celtics defensive strategy. Here, the Knicks saw it as a mismatch, which says something about their knowledge of opposing personnel. It should be known by now that Boston willingly throws Holiday on bigs and that he handles them effectively. Just going to it like it's a mismatch might work here or there, but it's not a high-percentage play.
With Boston able to cover Towns with one of three different players outside of Porzingis, it allows Porzingis to roam, deter drives, and help, even if the Towns cover flips to New York's favor.
Towns got the step on Tatum but Porzingis was there for the block. No one cared about where Hart was. When Luke Kornet checked into the game, he gave Hart the same treatment.
Kornet was there when OG Anunoby tried to spin back to the middle, so Anunoby kept going instead of shooting. It doesn't go into the books as anything, but that's rim and paint protection. Anunoby looked to be setting up a fadeaway jumper from eight feet away but instead he gave it up to Hart, a non-shooter who bricked a 3-pointer.
Shout out to Kornet's defense and footwork on this play. His positioning was excellent, he knew what he was willing to give up, and it worked. He was also very aware of Hart the whole time, which allowed him to get back out and challenge the 3-pointer rather than give him a dare shot.
Again, here's rim protection without a block or a shot attempt. Kornet ditched Hart to stop Brunson. He then slid over to deter Anunoby. Then Horford picked up Hart, who forced a shot up.
That shot is the product of frustration. No one on the Knicks at that point of the game had gotten a good look at that point, they were working really hard to get tough shots, and the Celtics were already starting to build a big lead. The defensive strategy was not only taking its toll on the Knicks by taking shots away from them, it was starting to wear on them mentally.
There are potential downsides to this kind of defense. Ignoring a player like Hart can leave him open for cuts and offensive rebounds.
If Hart was more aggressive on his cuts, and if the Knicks were better about looking for him, he might have made the Celtics pay more. Also, there has to be an emphasis on finding Hart so he's not getting putbacks.
The last thing we saw in that clip was Hart in transition. The key for any half-court defense, especially one that relies on matchups like this, is hitting shots and getting back to set up. This is what Joe Mazzulla means when he talks about everything being connected.
If the Celtics were cold from the floor in this game, the Knicks would have had more chances to run and avoid this matchup hell. If you understand how important it is to get the right matchups so Porzingis can roam, then you understand the importance of making shots so Knicks have to pull the ball out of the net and the Celtics can get matched up properly.
This is partly why the Knicks made a couple of runs in this game. The third-quarter run especially highlighted how Boston's settling for shots instead of moving the ball led to opportunities for the Knicks. Suddenly, guys were free to get looks they liked instead of fighting for every inch of space on the floor. The Knicks had 20 points in the paint in the first half and then 18 in the third quarter. The Celtics shot 53.2% in the first half but 40.9% in the third.
The other part was New York hitting 3-pointers. The Celtics won the first quarter 38-19 and the second quarter 26-24 but lost the third quarter 39-25. The Knicks were 5-17 from 3 in the first half but 6-9 in the third quarter. Go back to the first clip here and I'd tell Brunson in the film session to shoot that 3-pointer instead of faking it.
This is why the Celtics have so many problems with the Indiana Pacers. Indiana has shooting all over the floor and if the Celtics go cold at all, they will run and shoot before anyone knows what happened. Some people think the best way to beat the Celtics is with power, but it's with speed and shooting.
The Celtics play at the fifth-lowest pace in the NBA, with 97.7 possessions per game. Indiana is at nearly 101, which gives them a few more opportunities to score. If the Pacers are able to maximize those extra possessions with made shots, then that's like spotting them points heading into the game.
Most teams put someone on the floor who struggles to shoot more than the others. If the Celtics run good offense and get back to set their defense, they can make teams pay for doing so. This is partly why the Cavaliers got De'Andre Hunter. Yes, he can defend Boston's wings, but he also needs to be accounted for on the offensive end. It makes the Cavs harder to guard. That's the kind of move the Cavs had to make to give themselves a chance.
The second a weak link hits the floor, the Celtics pounce on it, and they can do it on both ends of the floor. The Knicks have too many of those, which is why the Celtics can dominate them in every matchup. Their strength is their offense, and the Celtics can shut it down pretty easily because of guys like Hart.