Boston Celtics center Robert Williams III is expected to miss 4-6 weeks as he undergoes arthroscopic knee surgery, as first reported by Sean Deveney. The procedure is meant to clean up Williams' knee and should have him back in the lineup early in the regular season, but it will likely keep him out of training camp and the preseason for Boston. 

Williams has a lengthy injury history, and most notably, he suffered a torn meniscus last season that kept him out of the end of the regular season while limiting him in the playoffs. Williams is very reliant on his athleticism. He is one of the NBA's premier rim-protectors and overall defenders, so getting him back up to 100 percent physically is absolutely essential.

The Celtics started last season 23-24, but skyrocketed up to the top of the standings when they tweaked Williams' role defensively to allow him more flexibility to roam around and make plays. The Celtics wound up finishing with the NBA's No. 1 defense, and had Williams remained healthy, it is possible that he, not teammate Marcus Smart, would have won the league's Defensive Player of the Year award.

His absence is yet another injury Boston will now need to deal with. The Celtics also lost forward Danilo Gallinari to a torn ACL earlier in the offseason while he was playing for the Italian National Team. With Daniel Theis traded in the offseason, the Celtics will now have to lean on Al Horford and Grant Williams for even more minutes early in the season.