Boston Celtics centre Robert Williams III reportedly will miss between 4-to-6 weeks after undergoing arthroscopic left knee surgery this week, according to ESPN's Adrian Wojnarowski.

It is the second surgery on the same knee in six months for Williams, who had a meniscus procedure performed March 30. That specific surgery enabled Williams to recover quicker and return to the court for Boston’s run to the NBA Finals.

The 24-year-old Williams injured the knee in a win over the Minnesota Timberwolves on March 27, forcing him to miss the final seven regular-season games and Boston's first two playoff contests.

He came off the bench in Games 3 and 4 of the Celtics' first-round sweep of the Brooklyn Nets, and started the first three games of the Eastern Conference semi-final series with the Milwaukee Bucks before suffering a bone bruise in the same knee in Game 3.

He missed the remainder of the seven-game series with the Bucks before returning to start Game 1 of the Eastern Conference finals against the Miami Heat.

Another knee injury sent him back to the bench for Game 3, but he then played the rest of Boston's seven-game series with the Heat and every game of Finals with the Golden State Warriors.

Williams has battled injuries throughout his four-year career and wasn't as effective in last season's playoffs compared to the regular season, averaging 7.7 points on 67.9% shooting, 6.2 rebounds and 2.2 blocks in 17 playoff games.

In 61 regular-season games last season, he averaged 10 points on 73.6% shooting, 9.6 boards and 2.2 blocks.

The Celtics went 40-21 in the regular season when he played and 11-10 when he didn't suit up.

Without one of the league's premier rim protectors, veteran Al Horford will be tasked with playing more minutes until Williams returns early in the regular season.

Boston tips off the 2022-23 season on October 18 against the rival Philadelphia 76ers.