Los Angeles Angels ace Garrett Richards was carted off the field on a stretcher in the second inning with what appeared to be a serious injury to his left knee Wednesday night against the Red Sox.

The Angels announced midgame that Richards had sustained a patellar injury to his left knee but did not speculate as to the severity of the injury. A club official said more information would be forthcoming. Richards was scheduled to fly back to Los Angeles on Thursday to be further evaluated.

With runners at first and second, Brock Holt hit a grounder to the right of first baseman Albert Pujols. He flipped to Erick Aybar for the force, while Richards sprinted to first to receive the return throw. But his knee collapsed underneath him a couple of steps from the bag. He clutched his left knee in agony while Angels trainers rushed to his side.

Richards remained down for several minutes while all the Angels players on the field gathered around him at first base, and Red Sox designated hitter David Ortiz came out of the Sox dugout and joined the group.