An MRI performed on the pitching shoulder of right-hander Tomo Ohka revealed a partial undersurface tear of his rotator cuff as well as a capsular injury. Ohka was placed on the 15-day disabled list and is expected to be out at least a month. Should the injury not heal through physical rehabilitation, surgery is possible that would sideline him for the remainder of the season. "It's tough," said general manager Doug Melvin. "He's a veteran, experienced guy. You felt every time out you have a chance to win the ball game. There's no substitute for that kind of experience."