BOSTON — Isaiah Thomas scored 22 of his 30 points in the fourth quarter in the Boston Celtics’ 90-83 victory over the Dallas Mavericks on Wednesday night.

Thomas scored 20 of Boston’s final 24 points to help the Celtics beat back a late Mavericks’ surge.

Avery Bradley added 18 points and 13 rebounds.

The Mavericks led 70-66 when Thomas scored Boston’s next 13 points to put the Celtics back in front 79-76.

Harrison Barnes led the Mavericks with 28 points. Wesley Matthews added 22.

Dallas, which was already missing several players because of injuries, lost two more. Starter Deron Williams exited in the second quarter with a left calf injury, and J.J. Barea was helped off the court in the fourth quarter after appearing to injure his left leg.

The Celtics built as much as a 12-point lead in the first half, but were slowed down by nine turnovers. It helped mask the Mavericks paltry shooting (14 for 45) in the opening 24 minutes.

Boston didn’t shoot much better (17 for 43), and was outscored by Dallas in the second quarter 14-10.