Castillo caught seven innings last night at Double-A Trenton and went hitless in three at-bats in his brief injury rehab assignment with the Bowie Baysox.
Castillo sustained a testicular injury on May 30 against the Yankees.
Peña also was designated for assignment on May 17, but he cleared waivers and accepted an outright assignment. He again has the right to refuse based on prior outrights.
The 40-man roster is back down to 39 players.
Jonathan Schoop is batting second.
Trey Mancini, who’s in left field tonight, leads the majors with a .438 (14-for-32) average with runners in scoring position. Adam Jones is second in the American League and tied for fifth in the majors at .400 (14-for-35).
For the Orioles
Seth Smith RF
Jonathan Schoop 2B
Adam Jones CF
Mark Trumbo DH
Chris Davis 1B
Trey Mancini LF
Welington Castillo C
J.J. Hardy SS
Rubén Tejada 3B
Chris Tillman RHP
Here are the starters for the White Sox series at Chicago: