After yet another surprising victory, maybe it's time to stop doubting the Celtics

BOSTON – Maybe we should stop being surprised by these Celtics, this Al Horford-fronted, Terry Rozier-led, Jayson Tatum-supported, Marcus Smart-inspired group. Maybe we shouldn’t be astonished when Boston, down another man — Jaylen Brown, he of the 18-point scoring average in the first round and the sore hamstring, is the latest to join the Celtics’ walking wounded — beats up on a team with superior talent. Maybe we should accept that Boston can win with whomever it has on the floor because of whom it has coaching on the sidelines.

On Monday, Philadelphia showed up at the TD Garden with a pair of franchise players, a top-five defense and shooters for every spot on the floor. They left 117-101 losers, buried by 83 total points from Rozier, Tatum and Horford and stymied by a Boston defense that is playing like the No. 1-ranked regular-season unit.

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“I never felt we were in the game,” Sixers coach Brett Brown said. “I never really felt it was a game.”

Boston is playing with house money, with Kyrie Irving, Gordon Hayward and Daniel Theis done for the season, but try telling anyone inside the Celtics’ locker room how great next year is going to be. Rozier isn’t Irving, but he believes that in coach Brad Stevens’ system, he can score like him. Rozier rolled into the arena in a throwback Drew Bledsoe jersey — a nod to his (allegedly) squashed beef with Milwaukee’s Eric Bledsoe — and for 35 minutes was the best guard on the floor. He killed the Sixers from beyond the 3-point line (7-of-9) and was part of the defensive effort that limited Philly to just 19.2 percent shooting from beyond the arc.

“We all got together yesterday and we had a plan,” Rozier said. “The plan was ways that we could stop these guys no matter who is on the court. We are well-coached and our coaches hold us accountable for taking care of business, and we hold each other accountable and that is the most important thing. That is why we don’t ever feed into the negative things that people say. We got each other, so no matter who is out there we are going to play hard and we are going to pay attention to details and take care of business.”

Rozier’s emergence has been a pleasant second-half surprise. Tatum? He’s been good all season. In a matchup of two of the NBA’s top rookies — Tatum is close to a lock to finish third in the Rookie of the Year voting behind Simmons and Utah’s Donovan Mitchell — Tatum’s 28 points won the day. Simmons’ final stat line wasn’t terrible (18 points, seven rebounds and six assists), but he was a miserable minus-21 and looked lost against a brilliant Boston defensive effort. When Simmons stepped to the free-throw line, the redshirt rookie was serenaded by “Not a rookie!” chants from the 18,624 in attendance. When Tatum went to the line, “He’s a rookie!” echoed in the building.

“[Tatum] has got a bounce,” Brown said. “When I watch him, he plays sort of older than his resume suggests. He’s got a lot of bounce and a lot of game. I thought tonight he scored in a variety of ways. I thought he was excellent.”

And what about that defense? With Bill Russell sitting courtside, the Celtics submitted a performance even Russell was impressed with. Injuries have shelved Boston’s offensive firepower, but the Celtics remain flush with high-level defenders, and they leaned on them, refusing to send double-teams to help on Simmons and Joel Embiid, willing to accept tough twos if they limited Philly’s uncontested threes.

“As a team we have to really be engaged, because those guys are so good,” Horford said. “As a team, we have to make sure we are there, helping each other. That’s what we have been doing all year. The defense has to be there for us to have any kind of chance of coming out of this series.”

That’s right: Down Irving, Hayward and, at least for Game 1, Brown, the Celtics are thinking conference finals and beyond. Philadelphia will make adjustments, but Boston is determined not to get buried by the same avalanche of 3-pointers that ended Miami, and the Celtics have enough bodies to make life difficult for Embiid and Simmons in the half-court. The 3-point shooting will cool off — the Celtics connected on 47.2 percent from distance Monday — but Smart (3-of-12 shooting) will be better and there is a good chance Brown will be back when the series resumes Thursday. Boston will continue to exploit mismatches (Marco Belinelli had a target on his back in Game 1) and lean on its ability to out-execute the Sixers in the half-court.

“No one [saw] this coming but us,” Smart said. “We have confidence in our team right now, and we’re playing great basketball.”

Indeed. In a seven-game series, talent usually wins out. But Milwaukee, with Giannis Antetokounmpo and a budding young roster, couldn’t take out Boston. If the Sixers don’t play better, they won’t either.

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