Before Ted Lilly pitched on a bum left knee last Monday night in Philadelphia, he said no one could talk him out of continuing in the rotation.

But the Cubs revealed before Friday's 8-5 victory over the Reds that the starter incurred soreness in his left shoulder after the Phillies pounded him and he may miss the next several weeks to let it heal.

Lilly was sent for an MRI-arthrogram Friday and was scratched from his scheduled start Saturday. Cubs sources indicate he will be placed on the 15-day disabled list Saturday with shoulder tendinitis.

The Cubs are hoping it's no more serious than that because a tear in the biceps area would force him to undergo arthroscopic surgery that would jeopardize his season.

"Obviously Teddy is a huge part of any success we've had the last few years [and] certainly a key component to the future," general manager Jim Hendry said. "Hopefully it won't be anything serious. We probably won't know the results of the test until [Saturday]."

Lilly, the Cubs only All-Star representative, leads the team with nine victories and 107 strikeouts. He had two stints on the DL with shoulder tendinitis in 2005 when he pitched for Toronto, but has remained healthy in 2 1/2 years with the Cubs.

If the Cubs lose Lilly for any significant length of time, they will be hard-pressed to replace him in the rotation.

"Oh gosh, we were just talking about getting [Ryan] Dempster back," manager Lou Piniella said. "We were happy about that, and all of a sudden, the Lilly situation [comes up]. It seems like every time we get a player, we lose one. But let's see what the MRI says on Theodore, and we can go from there."

Dempster is scheduled to return from his broken toe to start Tuesday's game against Houston. With no other left-handers in the rotation, the Cubs could move Sean Marshall back from the bullpen if Lilly is out for an extended period.

But recently acquired lefty reliever B.J. Ryan still is rehabbing in Arizona and isn't expected to report to Triple-A Iowa until Tuesday or Wednesday.

Then he likely would have another week or so before he would be ready to be called up to the Cubs.