Reliever Withrow sidelined after back spasms

GLENDALE, Ariz. -- Chris Withrow said he expects to be sidelined a few days with back spasms he experienced during his Friday bullpen session.

Withrow has had two previous episodes with a bulging disk that have sidelined him for extended periods, but he said the current discomfort is less than those and an MRI showed that the disk hasn't been further compromised.

"I don't think I made the existing injury worse," said Withrow, the club's 2007 first-round Draft pick, who is making a transition from starting pitcher to reliever.

Withrow, who with his wife survived an offseason rollover auto accident with only minor injuries, said this is the first time he's been injured while pitching. His earlier episodes were triggered by conditioning exercises and weight lifting.

"This is new for me, which is why I think it's not as bad," he said. "I'll take it easy a couple of days and make sure it doesn't flare up."