Making his first playoff start, the Celtics guard had 14 of his 23 points in the final 7:25 to help defeat the Milwaukee Bucks, 113-107, Sunday afternoon.

Jim Fenton The Enterprise @JFenton_ent

BOSTON – His first game as a starter in the NBA playoffs was not looking like it was going to be a memorable experience.

Through three quarters, Celtics guard Terry Rozier had only nine points on 4-for-13 shooting with five misses on six attempts from 3-point range.

Rozier, starting in place of the injured Kyrie Irving, turned his game around at the right time for the Celtics.

He hit a 3-pointer with 0.5 seconds to go in regulation that looked like it would give the Celtics a win over the Milwaukee Bucks, then scored eight points in overtime to help produce a 113-107 victory on Sunday afternoon.

Rozier had 23 points, 14 of them in the final 7:25, as the Celtics took a 1-0 series lead.

“I said it, I think, in the preseason,’’ said Jaylen Brown. “I said, ‘Terry, with the opportunity, could be one of the best point guards in the league.’ A lot of y’all looked at me like I was crazy.’’

Said coach Brad Stevens: “Terry’s a stud. Terry is a hard-nosed guy, he’s a competitive guy. He’s got great ability. He made some huge, huge plays there for us.’’

Rozier gave the Celtic a 99-96 lead with 0.5 seconds left in regulation, faking Eric Bledsoe and hitting a step-back 3-pointer. A Khris Middleton 3-pointer from 35 feet out at the buzzer forced OT.

“I kind of figured Bledsoe would bite and it allowed me to make a move and get to my step back three,’’ said Rozier.

He scored eight points in the extra session, hitting a 3-pointer and connecting on five of six free throws to seal the win.

“It’s been amazing,’’ said Rozier. “This is my third (year) in the league, third time in the playoffs and it just keeps getting better. It’s unfortunate what happened to our teammates throughout the whole year, but we still got each other and we still got to fight, still got to win.

“I just love playing with these guys and they just give me all the confidence in the world. But this year is probably the best one, plus I’m starting, so it’s like a dream.’’

Tatum a hit in debut: Rookie Jayson Tatum had 19 points and 10 rebounds with three steals in his first playoff game. He became the third Celtics rookie to record a double-double in his first postseason game, joining Bill Russell and Tommy Heinsohn (both on March 21, 1957).

Tatum’s 19 points are tied for third with Heinsohn for the most scored by a Celtics’ rookie in his debut playoff game, behind Frank Ramsey (25) and Kevin McHale (21), who was on hand Sunday working the TNT telecast.

“I was excited, but I wasn’t nervous at all,’’ said Tatum. “It was a lot of fun. I’ve always dreamed of this moment playing in my first playoff game. It helped we were at home and we had our home crowd behind us and we got our first win.’’

20-point club: The Celtics had four players score at least 20 points in a playoff game for the first time since April 28, 1991.

Al Horford led the way with 24 followed by Rozier (23), Marcus Morris (21) and Brown (20).

The last time it happened was against the Indiana Pacers in the opening round, a Game 2 loss. Reggie Lewis, Robert Parish, Brian Shaw and McHale all had at least 20 with Larry Bird scoring 18 points to go with 10 assists.

Around the rim: Marcus Smart was on the court shooting prior to the game for the first time since undergoing surgery on his thumb. Smart said he could be back if the series goes to a Game 7 a week from Saturday. … Irving was spotted on the Celtics bench in the first half, his first appearance since a second knee procedure. … The Celtics used a nine-man rotation with Greg Monroe (one point, three minutes) going only 10 minutes. … The Celtics improved to 23-20 in overtime playoff games.