"He looked real good in my opinion," manager Bob Geren said. "He said he felt good, and I thought his velocity was way up there. We didn't want to put a gun on a guy throwing for the first time, but it looked full speed to me, it really did.
"By the look and by the swings, it was very, very encouraging."
Bailey's next step will be another round of batting practice, possibly with the incorporation of breaking balls. Bailey has only been getting a feel for his breaking pitches from flat ground, and he'll have to take them to the mound before he can begin a Minor League rehab assignment.
The A's right-hander could potentially return by June. In the meantime, Geren will continue to rely on lefty Brian Fuentes for closer duties.
Fuentes has appeared in each of the past three games and five of the last six, making him unavailable for Wednesday's contest against the Indians following his loss Tuesday, when he gave up three ninth-inning runs while recording just one out.
Still, the veteran hurler has seven saves this season, which ranks fourth in the American League, and 190 since 2005, which are the most by a left-handed reliever in the Majors over that span.
Overall, the A's bullpen entered Wednesday's game with a 1.96 ERA over its past 15 games, including eight in which it has not allowed a run. The 'pen is also tied for second in the AL and sixth in the Majors with a 2.88 ERA this season.