First baseman Lance Berkman found it difficult to sleep Saturday night, not because of resulting pain from a right knee injury but because of what may result from Monday's finding.

The Cardinals and Berkman have yet to offer specifics about an injury caused by Berkman stretching for a routine throw from shortstop Rafael Furcal. Berkman felt continued stiffness in the leg Sunday afternoon and admitting contemplating the range of problems that Monday's magnetic resonance imaging might find.

Berkman said immediately after Saturday's game that he did feel a sensation similar to what he experienced when he tore his right anterior cruciate ligament in November 2005. Sunday, he couldn't dismiss the possibility and its implications.

"If I've re-torn my ACL or something like that, I'd certainly get it fixed but you don't know how psychologically you're going to come back from something like that," Berkman said. "I'm not talking from the standpoint of being scared of hurting it again. I'm talking about doing everything it takes to come back and play again at an elite level. I think that's a legitimate question I'm going to have to answer if, in fact, it turns out to be something more serious than we hope that it is.