Hiraldo (shoulder) will begin a rehab assignment Tuesday at High-A Frederick, Roch Kubatko of MASNSports.com reports.
Hiraldo had been in line to make his first rehab appearance Sunday, but a rainout pushed him back a couple days in the schedule. The 30-year-old reliever has been on the injured list since April 5 due to right shoulder inflammation and could need several appearances in the minors to knock off rust and hone his command, so it wouldn't be surprising if the Orioles waited until after the All-Star break to activate him.