Boston Celtics center Robert Williams III will undergo arthroscopic surgery this week on the same knee that required a meniscus procedure prior to his team's run to the NBA Finals, per ESPN's Adrian Wojnarowski.

Williams, 24, is reportedly expected to miss 4-6 weeks following a second surgery on his left knee in six months. Celtics team physician Dr. Tony Schena removed a partial tear in his left meniscus on March 30.

Williams initially suffered the injury during a victory against the Minnesota Timberwolves on March 27. He and the team weighed multiple surgical options, settling on the removal of the torn portion of the cartilage. That surgery allowed Williams to return sooner than expected. He came off the bench in Game 3 of the Celtics' first-round playoff series against the Brooklyn Nets on April 23, less than four weeks from the injury.

He played Boston's next five games, returning to the starting lineup, before suffering a bone bruise in the same knee during Game 3 of the Eastern Conference semifinals. He missed the final four games of the series Milwaukee Bucks, only to return for Game 1 of the conference finals. He missed just one more game in the playoffs, despite a collision between his knee and teammate Marcus Smart in Game 2 of the Finals.

Williams was hardly the same player upon his return, showing only glimpses of the athleticism that allowed him to create space with his verticality on offense and close gaps with quickness and verticality on defense.

Williams' development as an All-Defensive center earlier this year helped transform the Celtics from a sub-.500 team at midseason into a title contender. First-year Boston head coach Ime Udoka repositioned Williams as a roving baseline defender, toggling him between rim protection and corner 3-point defense.

The Celtics' starting lineup of Williams, Smart, Jaylen Brown, Jayson Tatum and Al Horford outscored opponents by 24.6 points per 100 possessions and logged a 27-7 record together in the regular season.

Should Williams not return in four weeks, Boston will begin this coming regular season on Oct. 18 with a shallow frontcourt. The Celtics traded reserve center Daniel Theis to the Indiana Pacers in the deal for guard Malcolm Brogdon over the summer. The 36-year-old Horford started at power forward last season and split his 29 minutes per game with stints at center. Free-agent signing Danilo Gallinari, who expected to fill minutes as a small-ball center, suffered a torn ACL in his left knee during a FIBA World Cup qualifier.

Luke Kornet is the only other center on the roster with guaranteed salary on his NBA contract. Grant Williams can play up a position, although the Celtics avoided playing him significant minutes at center. Two-way signee Mfiondu Kabengele and training camp invitee Noah Vonleh, both former lottery picks, will see an increased opportunity to earn playing time early for Boston, the league's preseason title favorite.

More concerning is the longterm impact for Williams. He fell to the 27th pick in the 2018 NBA draft due to concerns about the potential for chronic injuries to both of his knees. The Celtics have been cautious with Williams early in his career, holding him to fewer than 20 minutes per game for his first three seasons, when he averaged 38 appearances a year. His workload increased to 30 minutes per game this season, resulting in career-high averages of 10 points, 9.6 rebounds, 2.2 blocks and two assists, but he limped to the finish.

Williams is entering the first season of a four-year, $48 million contract extension he signed in August 2021.

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Ben Rohrbach is a staff writer for Yahoo Sports. Have a tip? Email him at rohrbach_ben@yahoo.com or follow him on Twitter! Follow @brohrbach