BOSTON — Celtics big man Robert Williams III will be available to play when Boston hosts the Bucks Sunday in Game 7 of their Eastern Conference semifinals matchup.

Williams has missed three straight games with soreness and a bone bruise in his surgically repaired left knee. He played the first three games of the series and has missed the past three.

Boston Coach Ime Udoka said Williams won’t start and would be used as needed. Grant Williams will remain in the starting lineup.

Williams has averaged 8.7 points and 5.6 rebounds during this series. Those are below his regular-season averages (10 points and 9.6 rebounds).

But Boston is hoping his presence will be boost to its defense as it tries to slow down Milwaukee’s Giannis Antetokounmpo, who is averaging 35.3 points, 13.8 rebounds and 6.8 assists in this series.

Sunday’s winner will take on the Heat in the Eastern Conference finals. That series will begin Tuesday in Miami.