BOSTON (AP) — Red Sox pitcher Steven Wright will miss the rest of the season after having surgery to restore cartilage in his left knee.

The team says the right-handed knuckleballer had the procedure on Monday.

Boston manager John Farrell said last week that no one specific thing caused Wright’s injury. The 2016 All-Star had some issues during spring training, then struggled at the start of the regular season. Recently he complained of discomfort in the knee before going on the disabled list on May 2.

In five starts this season, Wright was 1-3 with an 8.25 ERA.

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