Baltimore ? Orioles shortstop Mike Bordick rose from the ground during Monday’s game concerned about his head. He found out later that a more serious problem existed in his right leg, which will force him on the disabled list for the second time in two seasons.

A magnetic resonance imaging test and further examination Tuesday revealed a hairline fracture in his kneecap. Bordick’s leg will be immobilized for three weeks before the club re-evaluates the injury.

Bordick slid into Seattle shortstop Carlos Guillen after being picked off first base in the sixth inning of Monday’s 6-5 victory. His head slammed into Guillen’s leg, causing him to lie on his back for several seconds and bringing trainer Richie Bancells from the dugout. Bordick’s knee also collided with Guillen’s shin, which wasn’t apparent to him until attempting to stand.

The injury removes the Orioles’ most reliable defensive player from their lineup. He leads all shortstops with a .998 fielding percentage.