Jayson Tatum’s reintegration has gone more smoothly than the Celtics star expected.

Tatum, now six weeks removed from his return from Achilles surgery, was asked Friday whether he’s surprised himself with his performance thus far.

“The short answer,” he replied, “would be yes.”

Over his 16 regular-season appearances, Tatum averaged 21.8 points, 10.0 rebounds, 5.3 assists and 1.4 steals per game. His scoring output hasn’t returned to its pre-injury standard, but he’s rebounded at an elite rate, operated well as a facilitator and led the team in total steals during that stretch.

The Celtics, who far exceeded expectations during their 62 games without Tatum, are 13-3 with the four-time All-NBA first-teamer in the lineup.

“But with that,” Tatum continued, “there’s a quick turnover of, obviously you want more. And when you’re not 100% yourself yet, obviously it’s only been — I played 16 games. It can be frustrating at times, but you’ve got to just take a step back and be proud of the fact of what you were able to accomplish — of just coming back — and then everything on top of that has been icing on the cake.”

Celtics head coach Joe Mazzulla said Tatum is “getting better and better.”

“I think he’s given us exactly what we needed and then some, especially on the offensive end, reading the game and rebounding,” Mazzulla said Wednesday. “Just the mentality. It’s been a credit to him working to get back. All he cares about is getting better and winning, and that’s been big for us. He’s helped us on the defensive glass, he’s helped us on offensive reads, and he just continues to be as competitive as possible.

“Quite honestly, I think it’s pretty impressive he’s gotten back to the level that he is as fast as he’s done it while also keeping the main thing, the main thing, which is remaining healthy and giving us the best chance to win every night and being part of a team. It’s a credit to him.”

Tatum, who ruptured his Achilles in Game 4 of last year’s Eastern Conference semifinals against New York, enters Boston’s first-round series against the Philadelphia 76ers with no physical limitations. He shed his minutes restriction weeks ago, logging a season-high 40 minutes in his final regular-season outing (a 112-106 Celtics loss in Tatum’s cathartic return to Madison Square Garden).

Ahead of Game 1 against Philadelphia, which is set for 1 p.m. on Sunday at TD Garden, Tatum said he enters his eighth career postseason with “more of a sense of gratitude than ever.”

“I’m excited,” Tatum said. “My perspective has changed these last 48 weeks. I remember when I got injured, there was a lot of uncertainty. The playoffs wasn’t a sure thing. And now that I get that opportunity, I couldn’t be more happy.”

C’s keying on Maxey

With 76ers center Joel Embiid’s postseason status unclear following his emergency appendectomy last week, the Celtics’ primary focus as their first-round series tips off will be containing Philly’s other top star, Tyrese Maxey.

Mazzulla said Boston’s defense will need to be “elite” against the All-Star guard, with a particular emphasis on limiting his transition opportunities and keeping him off the foul line. Maxey, the NBA’s fifth-leading scorer during the regular season, averaged 30.0 points, 8.8 assists and 7.3 free-throw attempts per game across his four matchups with the Celtics.

“He obviously can get to any spot that he wants,” Mazzulla said. “I think the things that he tests is transition and free throws. You could look up at a box score and he can have 40 points, and half of those could be in transition or at the free-throw line. So he tests your discipline to be able to defend him. Not only in transition, trying to keep him off the free-throw line, but also he can score at all three levels. He can get layups, he can shoot pull-up twos and he can create separation on threes.

“So we have to be disciplined in what we’re taking away and what we’re willing to live with, and we’ve got to be great at the things we can control. And then we need elite individual defense throughout games, which our guys are capable of.”

Reserve wing Jordan Walsh had success against Maxey in previous Celtics-Sixers games, holding him to four points on 1-of-10 shooting with one shooting foul during the regular season. Baylor Scheierman drew the primary matchup against Maxey in the teams’ most recent meeting, and Maxey shot 3-for-10 with one drawn foul against him as the Celtics won 114-98 on March 1. Maxey totaled 33 points in that game but attempted 34 field goals.

“I mean, he’s a really good player, obviously, getting close to 30 a game,” Celtics wing Sam Hauser said. “What makes him really good is he’s super fast, and he can stop on a dime, and that’s hard to guard. He creates a lot for their team, and we just do our best to make it as difficult as we can on him. It’s not going to be perfect every time. He’s definitely going to score some buckets, but if we’re making him work for it, I think that’s a win for us.”

Historic rivalry

This will be the 23rd postseason meeting between the Celtics and 76ers, by far the most between any two NBA franchises. No other teams have met more than 15 times in the playoffs.

The teams’ first came way back in 1952, when Bob Cousy and the C’s beat the then-Syracuse Nationals 2-0 in the Eastern Division semifinals. Their most recent was the 2023 East semis, during which Boston rallied from a 3-2 series deficit to win in seven.

Mazzulla said he’s sure the decades-long rivalry “means a ton to the fans.”

“You can’t run from the fact that, obviously, these two teams have played against each other a long time,” he said. “You have to have an understanding of that, but you just can’t be distracted by the stuff that we have to execute on both ends of the floor and focusing on us being our best and knowing we’re going to get their best.”

Tatum has played 16 career playoff games against the Sixers, including his 51-point Game 7 masterpiece three years ago. Co-star Jaylen Brown has played 15.