NEW YORK - Grant Williams scored a career-high 27 points and hit seven three-pointers, helping the Boston Celtics defeat the Milwaukee Bucks 109-81 in Game 7 of the NBA Eastern Conference semifinals on Sunday to end the Bucks' title defense.

The Celtics trailed by six in the first quarter. Jayson Tatum and Jaylen Brown helped the Celtics take the lead in the midway of the second quarter, but Giannis Antetokounmpo turned the game into a seesaw battle after a 6-0 dash for the Bucks. Before the break, the Celtics led 48-43.

The Celtics built a two-digit-advantage in the third quarter. Payton Pritchard's three-pointer enlarged the advantage over 20 points in the final quarter, putting the game beyond the Bucks' reach.

The Celtics hit 22 three-pointers in the game, with Tatum contributing 23 points and eight assists.

For the Bucks, Antetokounmpo pocketed 25 points, 20 rebounds and nine assists, and Brook Lopez had a double-double with 15 points and 10 rebounds.

In Sunday's other game, last season's runners-up the Phoenix Suns lost to the Dallas Mavericks 123-90, seeing Luka Doncic and his teammates advance to the Western Conference finals.

Doncic gave the Mavericks an early lead, making his first three shots. Dallas led by 10 in the first quarter. The Suns, who won 64 games in the regular season, only pocketed 10 points in the second session, giving their rivals a 57-27 lead at halftime.

Doncic and Jalen Brunson kept firing beyond the arc midway through the third quarter, helping the Mavericks grab a 42-point advantage before the last quarter to stun the Suns fans. The Western Conference's top seeds never led at any point during the game.

Doncic hit a game-best 35 points and 10 rebounds. For the Suns, All-Star guard Chris Paul only had 10 points and four assists, while Booker had 11 points and shot 3 of 14.