CHICAGO - Royals centre fielder Lorenzo Cain exited Wednesday night's game against the Chicago White Sox and is day to day for playoff-bound Kansas City with a bruised right knee after fouling a pitch off himself.

Cain collapsed to the ground and writhed in pain after the ball struck him around the right knee cap. He remained on the ground for several minutes while being examined by a team trainer. Cain briefly remained in the game, but struggled to get down the first base line after grounding out to White Sox third baseman Mike Olt.

Cain, who was 0 for 4 Wednesday before being forced out by the injury, was replaced in centre by Jarrod Dyson.

Cain is batting .303 with 16 homers and 28 stolen bases this season.