Philadelphia 76ers vs Boston Celtics Box Score on Apr 30, 2018

Rozier scored a career-playoff-high 29 points and added eight rebounds and six assists. Tatum had a personal-playoff-best 28 points, and Horford tied his career playoff scoring mark with 26 as the Celtics took a 1-0 lead in the best-of-seven series.

"My confidence is everything," Rozier told TNT after besting by three points his prior career playoff high set Saturday in Game 7 against the Milwaukee Bucks. "My teammates believe in me, my coaches believe in me, so you know I just want to keep it going."

Celtics coach Brad Stevens said of Horford, according to NBA.com, "I feel like he's really locked in. He's done a good job of knowing when to roll and post and play an interior spot, and then knowing when to pop and space."

Joel Embiid had 31 points, 13 rebounds and five assists for Philadelphia. JJ Redick scored 20, and Ben Simmons totaled 18 points, seven boards and six assists with seven turnovers for the 76ers, who took just their second loss since March 13. Philadelphia eliminated the Miami Heat in five games in the first round of the playoffs.

Game 2 is Thursday night in Boston.

The Celtics made 17 of 35 3-point attempts (48.6 percent), while the Sixers sank just 5 of 26 shots from long range (19.2 percent).

"It starts on defense," Embiid said. "I thought I was (lousy). I thought we were all bad tonight. That's not who we are, definitely. I think when everybody's on, we're the best defensive team in the game. There's a lot of stuff that we game-planned that we didn't execute."

Philadelphia coach Brett Brown added, "I thought this was one of our poorer defensive games. I think to look at this game, defensively, offensively, this isn't who we are. This is a very poor game from us, and I give credit to the Celtics for producing that."

It's the first postseason matchup between the 76ers and Celtics since the 2011-12 East semifinals, when Boston beat Philadelphia in seven games. That was the 76ers' last second-round playoff appearance before this season.

The Celtics won three of four regular-season games against the 76ers, outscoring them by 23 points collectively. However, all four matchups came before the All-Star break and before Boston star Kyrie Irving sustained a season-ending knee injury.

Boston's Jaylen Brown (right hamstring strain) missed the Monday game after being listed as a game-time decision. Brown, who is the Celtics' second-leading scorer (17.9 points per game) this postseason, was injured Saturday.

Marcus Smart beat Embiid to a rebound and converted an acrobatic three-point play with 40.9 seconds left in the third quarter, putting the Celtics up by 17. However, the 76ers pulled within 87-75 entering the fourth.

Philadelphia was unable to get the deficit below eight in the fourth.

Boston led 56-45 at halftime after leading by as many as 13 in the second quarter. The Celtics were up 25-22 after the first.

Legendary Celtics center Bill Russell attended the game and sat courtside.

--Field Level Media