Celtics head coach Ime Udoka said Sunday that Williams tweaked his knee during Game 4, but Boston is "optimistic" he'll be available for Monday's Game 5, Anthony Slater of The Athletic reports.
Williams continues to deal with knee pain since returning from nearly a month-long absence following meniscus surgery at the end of March. Despite the lingering issue, the talented big man has appeared in 15 postseason games, including eight straight. During that stretch, Williams has averaged 7.1 points, 6.6 rebounds and 2.4 blocks across 22.8 minutes per game.