Boston’s Robert Williams III keeps the ball away from Orlando’s Moritz Wagner during the Celtics’ 117-109 loss on Friday in Boston. MIchael Dwyer/Associated Press

BOSTON — Moritz Wagner scored 25 points and Paolo Banchero added 20 as the Orlando Magic beat the NBA-leading Boston Celtics 117-109 on Friday night.

Franz Wagner scored 19 points as Orlando won its fifth straight game. The Magic outrebounded the Celtics 53-38 and held the lead for the final 37 minutes of the game.

Jayson Tatum scored 31 points and Jaylen Brown 26 as Boston (22-8) lost for the third time in four games.

Boston’s Robert Williams played in his first game since the NBA Finals after undergoing surgery on his left knee during the preseason and finished with nine points and five rebounds in 18 minutes.

Helped by two 3-pointers in the opening minutes from Al Horford, the Celtics jumped out to a 14-5 lead against a team with the third-worst record in the Eastern Conference. The Magic surged back, closing the opening quarter with a 15-4 run that was capped with a buzzer-beating 3-pointer by Banchero.

Orlando kept the pressure on Boston, leading 62-54 at halftime and extending the lead to 19 points early in the third quarter. The Celtics cut their deficit to single digits on a few occasions, but the Magic remained comfortably ahead.

Markelle Fultz scored five straight, including a 15-foot pullup jumper that gave the Magic a 108-96 lead with 3:55 remaining. He scored 12 points before fouling out.

WILLIAMS’ RETURN

Williams’ surgery in the offseason was his second procedure on the same knee in a six-month span. The 25-year-old was upgraded to questionable on Thursday, with interim head coach Joe Mazzulla confirming before Friday’s game that “there isn’t a minutes restriction” concerning Williams, who came off the bench against the Magic.

Williams received a standing ovation at 7:03 of the first quarter. He connected on an alley-oop slam dunk on a pass from Marcus Smart, but picked up three fouls over a four-minute span. His best stretch of the game came in the third quarter, when he slammed home a miss by Brown and seconds later connected with Tatum for a dunk.

SILAS REMEMBERED

Boston honored former player Paul Silas, who died last Saturday, with a moment of silence before the game. Silas packed a lot into his four seasons with the Celtics (1972-76). He was part of two NBA championships (1974, 1976) and appeared in the All-Star Game in 1975.

TIP-INS:

Magic: Orlando entered Friday with one road win in 12 tries. … With 32 points in the first quarter and 30 points in the second, the Magic have scored 30-plus points in a single quarter 35 times this season.

Celtics: Horford returned to the lineup on Friday after missing the previous five games. He wasn’t around for the finish after being assessed a flagrant-two foul at 10:39 of the third quarter. At the time of the ejection, Horford had six points and six rebounds in 16 minutes. … Friday marked the start of a seven-game homestand for Boston after a six-game trip.