From the press release:
The Orioles announced today that they have reinstated RHP ALFREDO SIMON from the 15-day disabled list, where he was placed retroactive to June 13 with a right hamstring strain. To open up a spot for him on the 25-man roster, LHP CLAY RAPADA has been designated for assignment.
Simon has appeared in five games for the Orioles this season, going 1-1 with a 3.14 ERA (14.1IP, 5ER). He pitched 3.0 innings or more in each of his last three outings.
Rapada appeared in 22 games for the Orioles, pitching to a 7.30 ERA (12.1IP, 10ER). He held left-handers to a .114 average (4-35) but allowed right-handers to hit .692 (9-13) against him.
Rapada has had his troubles in the bullpen, but when restricted to only facing lefties he had done pretty well. Left-handed batters went 4-for-35 against Rapada with only one home run and no doubles. It's no big loss, really, but I was expecting to see Berken or Bergesen sent back down.