Cain threw a bullpen session Tuesday for the first time since undergoing elbow surgery, John Shea of the San Francisco Chronicle reports. Cain threw 20 pitches in his bullpen session, marking the first time he's thrown off a mound since going on the disabled list last season. He's expected to throw 3-to-4 more bullpen sessions before facing live batters. His next bullpen session is slated for Friday.