The Orioles' top position player prospect, Jonathan Schoop, was placed on the seven-day minor league disabled list Thursday with a lower back strain.
The 21-year-old Schoop, who raised his stock after strong offseason performances in the Arizona Fall League and the World Baseball Classic, is hitting .268/.331/.386 with three homers and 18 RBIs in 34 games at Triple-A Norfolk.
The injury isn't expected to be serious. Schoop is the Orioles' No. 3 prospect according to Baseball America behind pitchers Dylan Bundy and Kevin Gausman.
Left-hander Tsuyoshi Wada threw four innings in his first minor league rehab start on Thursday for Norfolk. He allowed four runs -- three earned -- on three hits, striking out five and walking two with one wild pitch.
Three of Wada's first six outs came by strikeout, but he also allowed a pair of homers in the fourth inning that accounted for all of his runs.
Wada was scheduled to throw either six innings or 75 to 85 pitches, so he was removed after four innings because he had thrown 78 pitches (45 strikes).
He is working his way back from Tommy John surgery last May.