The Reds have released this statement:

LF Ryan Ludwick will have surgery tomorrow to repair torn cartilage in his right shoulder. He will go on the 15-day disabled list, and a corresponding roster move will be made prior to tomorrow night’s game.

No mention of how long he’s expected to be out.

Lance McAlister is saying that John Fay is predicting either Denis Phipps or Derrick Robinson will be called up.