Red Sox center fielder Jackie Bradley Jr. is awaiting the result of tests to determine the severity of his right knee injury.

Bradley lost his footing and twisted his knee as he rounded first base on a fly out in the ninth inning Saturday. His knee appeared to be stable during an initial examination by on-call doctors at Comerica Park, and Bradley expected to "absolutely" be able to play Sunday. But the plans changed when Bradley's knee stiffened and swelled up overnight.