San Diego, CA -- (Sports Network) - San Diego Padres ace Jake Peavy is headed to the 15-day disabled list with a strained flexor muscle in his right arm.

Peavy was supposed to take the mound for the Padres' 8-2 loss to the Cardinals Monday night, but was scratched on Sunday and had an MRI on Monday, which revealed the strain.

"You always fear the worst, this time it wasn't," San Diego manager Bud Black said following Monday's game. "Jake is out two weeks. We don't know the other end of that time frame."

The reigning NL Cy Young Award winner has a 4-3 record in nine starts this season, with a 2.91 earned run average and 60 strikeouts in 58 2/3 innings.

Lefty Wil Ledezma (0-1) got the start for the Padres on Monday, and was touched for four runs on five hits in four innings of work.