Oklahoma City Thunder point guard Russell Westbrook had arthroscopic surgery on his right knee, ESPN.com's Royce Young reported Wednesday.

Young described the procedure as "maintenance" for Westbrook after the All-Star guard was feeling stiffness in the knee. Young added that doctors will re-evaluate Westbrook in four weeks to determine when he'll be healthy enough to suit up for the Thunder.

Because Westbrook's return date is unclear, he could be unavailable for the start of the preseason.

Despite playing a bruising, attacking style, Westbrook has been seemingly indestructible over the past few seasons. In fact, he's missed a grand total of five games since the start of the 2015-16 season. 

Given Westbrook's status as the engine of OKC's offense, it's safe to say some adjustments will have to be made if his recovery lingers into the regular season, which starts Oct. 16 against the Golden State Warriors. 

Fortunately for Thunder head coach Billy Donovan, he has a capable backup in Dennis Schroder who can help steady the backcourt while Paul George would assume an even heavier share of the on-ball playmaking responsibilities.