When the Celtics open their regular season less than a month from Tuesday (they begin play on October 18 against the Sixers), they may have to do so without their full starting lineup. According to ESPN’s Adrian Wojnarowski, starting center Robert Williams will undergo an “arthroscopic procedure” on his left knee this week, and is expected to miss four-to-six weeks. Wojnarowski added that Williams is expected to be “back in the lineup early in the regular season.”

Williams first injured his left knee late last season, when he suffered a torn meniscus. The surgery he had at the time held him out of the early playoff games, and saw his playing time managed the rest of the way.

After being a rotational player for the first three seasons of his career, Williams stepped into a starting role last year. In 30 minutes per game with 61 starts, he averaged 10 points, 9.6 rebounds and 2.2 blocks per game and worked his way into the Defensive Player of the Year conversation before his injury. The Celtics were 40-21 when he was in the lineup, and 11-10 when he was out.

Without Williams, the Celtics will have a spot for a big man open up in their rotation behind Al Horford. Luke Kornet may be the favorite for that job, but the team signed a number of centers to small money and/or non-guarnateed contracts this summer who could compete for that role. Those players include Bruno Caboclo, Noah Vonleh, and Mifondu Kabengele.

The Celtics will hold their annual media day on this upcoming Monday, then begin training camp shortly after. Their preseason schedule begins Oct. 2.

Robert Williams career stats

Alex Barth is a writer and digital producer for 985TheSportsHub.com. Any opinions expressed do not necessarily reflect those of 98.5 The Sports Hub, Beasley Media Group, or any subsidiaries. Thoughts? Comments? Questions? Looking for a podcast guest? Let him know on Twitter @RealAlexBarth or via email at [email protected].