KANSAS CITY -- Royals left-hander John Bale suffered a setback in the first outing of his injury rehabilitation assignment with Double-A Northwest Arkansas.

Bale threw just seven pitches in relief against Springfield on Wednesday before he had to leave because of a cramp in his right glute. He gave up one hit and was charged with one run in two-thirds of an inning in a 14-9 loss.

Bale is returning after thyroid surgery during Spring Training.

Meantime, closer Joakim Soria said he was ready to pitch in Wednesday night's game against the Mariners. He was held out Tuesday night in an extra-innings game against the White Sox because of what the Royals called stiffness.

Shortstop Tony Pena was back in the clubhouse after undergoing surgery on Monday for a fractured hamate bone in his left hand. He can throw and run but cannot catch or bat a ball. He's expected to miss four to six weeks.

Reliever Doug Waechter, on a rehab assignment with Triple-A Omaha, has reported no problems after testing his strained right elbow in a game two days ago.