Kristaps Porzingis hit a dagger 3-pointer on a big night against his old team, and the Celtics claimed a hard-fought 115-112 OT victory against the Knicks on Tuesday. Here are the takeaways. 1. Kristaps Porzingis is having fun (still) For two years now, Porzingis has been very evidently having a great time when he plays at TD Garden. But on Tuesday, Porzingis appeared to be having an equally great time at Madison Square Garden. Porzingis continued to excel as he ramps up to the playoffs, pouring in 34 points on 11-for-19 shooting. Most notably, he buried eight 3-pointers including this pick-and-pop triple with Derrick White as Jalen Brunson crashed straight into him, which proved to be the difference in overtime. Porzingis also hit an absurd 3-pointer as part of a 13-point third quarter barrage. Jayson Tatum fumbled his dribble and the ball rolled to the middle of the “K” in the Knicks’ mid-court logo, where Porzingis scooped it up and launched it, burying the triple that put the Celtics up by seven. Porzingis isn’t a perfect matchup for Karl-Anthony Towns, who is more physical and also more than happy to launch triples that pull bigs away from the rim. Porzingis will also need to be very disciplined against the Knicks’ guards if the teams meet in a playoff series; Brunson is incredibly adept at drawing fouls, especially against players a foot taller than him. But Porzingis can take advantage of the Knicks’ defensive liabilities as well as his other star teammates, and when the matchup-heavy playoffs roll around, that will be a big deal. 2. Jayson Tatum had a lot of answers for the Knicks’ defense The Knicks threw a lot of different looks at Tatum, who came up with answers for most of them. In the first half, Tatum beat OG Anunoby multiple times out of the pick-and-roll when the Knicks’ wing tried to cheat high to force Tatum into the screen. Later in the game, the Celtics got Tatum onto Mikal Bridges multiple times, and Bridges had absolutely nothing for Tatum. The Celtics star spun past him to the rim in the first half, then buried four straight turnaround jumpers on Bridges in the second half. TNT broadcaster Reggie Miller called what Tatum was doing to Bridges “borderline child abuse” at one point, to which 1) we would argue that maybe child abuse isn’t something we want to introduce into common sports parlance but also 2) isn’t a great sign for the Knicks given what they gave up to get Bridges. In the fourth quarter and overtime, the Knicks started to stymy Tatum a bit by playing incredibly physical defense and daring the referees to make a call. The officials mostly let Anunoby play as physically as he wanted — something to watch if the teams meet in the postseason — but they didn’t let Towns get away with smacking Tatum in the forearm on a 3-pointer, which gave the Celtics a chance to tie the game (Tatum went 2-for-3 at the line). Then Tatum hit Anunoby with a stepback and stuck the triple to send the game to overtime. Tatum finished with 32 points on 22 shots to go with seven rebounds and five assists. He played 47 minutes, so presumably he won’t play Wednesday against the Magic, but add Tuesday to his list of brilliant performances this season. 3. Al Horford matters against the Knicks The Celtics won, but Towns was a tough matchup for Tatum, who got significant minutes on the Knicks’ star big man. Tatum is strong, but he couldn’t contain Towns in the paint, and Towns went off for 34 points on 14-for-21 shooting. The Celtics do have two players who play Towns tough: Jrue Holiday — who drew the assignment on several possessions and performed admirably — and Al Horford, who remains one of the best defenders against essentially any kind of big man in the NBA. Horford sat out Tuesday’s game with a right knee sprain, but he remains crucial to the Celtics’ playoff run. 4. Jaylen Brown sat out the fourth quarter Jaylen Brown didn’t look like himself in 22 minutes, and he finished the game with just six points on 2-for-8 shooting. Concerningly, Brown didn’t look like he had much explosiveness to create space, which is important both against the Knicks’ rangy wings and to take advantage against players like Brunson and Towns. Also concerning: Brown also sat the entire fourth quarter and overtime. “We just got what we needed to get out of him as he continues to push himself and test himself,” Joe Mazzulla told reporters afterward. “We’ve still got games left, so we got what we needed to get, what we needed to see, and we move forward.” Players need to play 20 minutes or more for a game to count toward their All-NBA chances. Brown has now played in 63 of the necessary 65 games to be eligible. The Celtics have three games remaining. For what it’s worth, the take here is that Brown is well within his rights to pursue an All-NBA selection. All-NBA matters quite a bit for a player who is building a potential Hall of Fame resume. Still, Brown’s performance Tuesday won’t lessen concerns about his knee. 5. The Knicks gave Carmelo Anthony a tribute video (and he gave us a meme) In a nice moment during the first quarter, the Knicks gave Carmelo Anthony a tribute video after the former Knicks star was selected to the Hall of Fame. Anthony, who was in attendance, appeared moved by the video and by the standing ovation that ensued. Late in overtime, however, Anthony also gave us a highly versatile meme when Towns rocketed a pass off Bridges, essentially clinching the win for the Knicks. Anthony’s exasperated expression afterward might have some staying power. 6. The Celtics have officially swept the Knicks in the regular season The Knicks really needed Tuesday’s win for a lot of reasons. A win would have cemented them in the No. 3 seed, and it would have given them their first win against one of the top three teams in the NBA (the Celtics, the Cavaliers, and the Thunder, against whom the Knicks are now 0-9). The Celtics really only needed Tuesday’s game to prevent the Knicks from getting it. They won anyway. That’s not to say the Celtics won without trying. The fact that they played Tatum 47 minutes in a game that had no bearing on their playoff seeding suggests that they too felt the potential psychological advantage of going 4-0 against a team they might meet in the Eastern Conference semifinals. But, the Celtics were without Horford for the entire game, they were without Brown for the fourth quarter, they were without Porzingis for half of overtime, and they were without anything to play for other than just trying to overcome another basketball team. And still, they were unshakeable in the clutch when the Knicks surged late, a machine that inexorably turns its gears toward a win. After four regular-season games, the Knicks simply don’t appear to have enough firepower to stop that machine. 7. The Celtics need one more win for 60 Winning 60 games in back-to-back years is hard. Winning 60 games in back-to-back years after winning a title — with the championship hangover and all of the nagging overuse injuries that come with success — is even harder. That the Celtics are on the verge of doing it again speaks to the mettle and genuine greatness of this team. However long this playoff run goes, the Celtics have done something special the last two years. 8. Two different kinds of back-to-backs The Celtics will play their second game in as many nights on Wednesday when they take on the Magic in Orlando. They will close their regular season with games against the Charlotte Hornets at TD Garden on Friday and Sunday. After that, the real season begins.