Celtics center Robert Williams out eight to 12 weeks following knee surgery

The bad news continues to pile up for the Boston Celtics.

The Celtics announced Friday that injured big Robert Williams underwent successful arthroscopic surgery on his left knee to remove loose bodies and address swelling. The 24-year-old is now expected to return to basketball activities in eight-to-12 weeks.

That is a pretty disappointing downgrade for Williams, as he was originally anticipated to miss only about half that time. Williams, who is Boston’s best shot-blocker and dunker, rushed back from meniscus surgery in his left knee last March so that he could participate in the team’s postseason run (during which the Celtics eventually made the Finals for the first time since 2010).

An eight-to-12-week timetable would place Williams’ return to basketball activities (not necessarily his return to game action) at some point in either November or December (the Celtics tip off the season on Oct. 18). There is still a reported possibility that Boston could sign a notable veteran center in Williams’ absence.