Terry Rozier added 16 points, Jaylen Brown had 14 and Marcus Morris had 10 for the Celtics, who can clinch the best-of-seven Eastern Conference quarterfinals series with a win in Game 6 on Thursday in Milwaukee.

Khris Middleton led the Bucks with 23 points while Jabari Parker had 17 and both Giannis Antetokounmpo and Eric Bledsoe scored 16. Antetokounmpo added 10 rebounds and nine assists. Milwaukee lost the first two games of the series in Boston before winning back-to-back games at home to even the series.

Horford produced his first 20-10 game as a Celtic.

"Just making tough plays down the stretch," Horford told NBC Sports Boston about the Celtics' victory. "We really couldn't pull away (and) they kept fighting, but our defense got the job done tonight."

Marcus Smart returned for the Celtics after missing the first four games of the series and the last 15 games of the regular season while recovering from right thumb surgery. Smart had nine points, five rebounds, four assists and three blocks off the bench.

John Henson (back soreness) missed his third straight game for Milwaukee.

The Celtics led by 11 entering the fourth quarter.

Antetokounmpo's two free throws with 7:33 remaining had the Bucks within 74-70, but Horford answered with a 3-pointer 20 seconds later and Morris' layup had the lead up to nine with 5:48 to go.

Middleton hit a fadeaway jumper and was fouled, but he missed the free throw as Milwaukee pulled within 84-79 entering the final minute.

After an uncontested Horford dunk made it 86-79 with 28.1 seconds left, Middleton knocked down a 3-pointer with 25.4 seconds on the clock to make it a four-point game.

Horford hit one of two free throws with 24.4 ticks to play before a Bledsoe jumper at the 19-second mark.

Rozier made four free throws in the final 16.4 seconds to seal it.

Boston was up 48-37 at halftime.

Smart checked in to a standing ovation from the crowd with 4:08 left in the first quarter and made an immediate impact, diving for a loose ball and later converting a three-point play to help the Celtics build a 23-15 lead after one.

--Field Level Media