The club has 10 days to trade Rapada, pass him through waivers and outright him to Triple-A Norfolk or release him.
The Sun's Jeff Zrebiec tweeted the roster move, and a team official just confirmed it.
Rapada was effective against left-handers, as advertised. They went 4-for-35 against him, with one home run, three walks and 13 strikeouts. However, right-handers were 9-for-13 with two doubles, one triple, two home runs, three walks and no strikeouts.
The Orioles apparently don't believe they can afford the luxury of carrying a left-handed specialist in their bullpen. They prefer the multiple innings that Simon provides, and someone who isn't as overmatched against righties.
Rapada signed a minor league deal Jan. 25 and had his contract purchased by the Orioles on April 18.
The 40-man roster is down to 39 players.
For the Orioles:
J.J. Hardy SS
Nick Markakis RF
Adam Jones CF
Vladimir Guerrero DH
Derrek Lee 1B
Matt Wieters C
Mark Reynolds 3B
Felix Pie LF
Blake Davis 2B
Chris Jakubauskas RHP