Ryu's early exit from Monday's game against the Cardinals was due to a strained left groin muscle, Bill Plunkett of The Orange County Register reports.
Ryu was pulled from Monday's game in the second inning with what turned out to be a strain to same groin that forced him out of action for three months after he tore it last season. It remains to be seen if he requires a trip to the injured list, but it could be in the cards for the left-hander.