MILWAUKEE — Things can turn, so quickly.

With the Boston Celtics winning the first two games of their first-round series with Milwaukee, the Bucks responded in Game 3. Khris Middleton scored 23 points, Giannis Antetokounmpo added 19 and the Bucks overwhelmed the Celtics 116-92 on Friday night to get their first win of the best-of-seven series.

Al Horford scored 16 for Boston, but the Celtics fell behind by 23 at halftime and got no closer than 76-62 with 3:06 left in the third quarter.

“We got into a hole. This is new for our group,” Horford said. “They had it going … and we really didn’t have an answer for them tonight.”

Milwaukee found its defense after a disheartening 14-point loss in Game 2, getting contributions from up and down the roster.

“We realized how important this game was … Everybody that played came in ready to go,” Antetokounmpo said.

The game was so well in hand that the Bucks closed out the victory with Antetokounmpo on the bench for much of the fourth quarter with five fouls.

Now Game 4 is Sunday in Milwaukee and the Celtics will need to get off to a much better start if they want to avoid going home with a 2-2 series tie.

The Bucks were the aggressors all night long in Game 3.

“The activity, if you take the stat sheet out of it, the activity and the energy that we brought … as you go through the game, that’s what you need, is the energy first,” Milwaukee Coach Joe Prunty said.

Milwaukee hustled for loose balls and stayed active around the paint, using its length to get deflections and disrupt Boston in the lane.

Nearly everything came together for Milwaukee.

Even Jabari Parker, who voiced displeasure this week after playing just 24 minutes over the first two games, was 7 of 12 from the field and played 30 minutes.

“Obviously, it was all in the first half,” Celtics Coach Brad Stevens said about his team’s downfall. “They were in such a rhythm offensively.”

Terry Rozier had five turnovers, but four came in a first quarter in which the Celtics fell behind 27-12. He also had nine assists, but after getting the best of Eric Bledsoe in the first two games, it was the Milwaukee guard with the edge on Friday night.

“There’s nothing about me and Bledsoe. There’s nothing that he did differently today,” Rozier said. “They punched us in the mouth early. We’ve got to do a better job of responding on Sunday, and we will.”

Boston held a 45-37 edge in rebounding, including 17-7 on the offensive glass. But the Celtics allowed the Bucks to shoot at least 57 percent for a second straight game.

Just because he played two seasons plus a fraction of a third for the Bucks doesn’t mean that Greg Monroe feels any more animus than usual for his opponent.

“No, man. Y’all keep asking me that,” he said with more than a hint of agitation. “You know how many people are playing their old teams? It’s really really not a big deal. I know you guys want it to be, but it’s the playoffs. I’m pretty sure that no matter who anyone is playing at this point, they want to win. It don’t matter. It’s no more incentive. Either you win or go home. It doesn’t matter if I’m playing another team I’ve never played for. We lose the series, we go home. That’s just how it is. We want to win the series. We want to win every game.”

But Monroe’s time in the Bucks system as a reserve undoubtedly helped him when it was time to fit in with the Celtics, who use him the same way.

“They’re a little bit similar. Bigs play a lot through the elbow,” he said. “That’s probably the thing that’s most similar in both offenses. Bigs handle the ball a lot at the elbow. I think I’m being used pretty much the same way.”