O'Flaherty missed 29 games with a strained left shoulder after struggling to the tune of an 11.57 ERA in eight appearances in April, but he still refuses to use it as an excuse.
"Sometimes you just suck," said O'Flaherty, smiling. "If you go out there and pitch, it's your job to get the job done. Maybe just location a little bit. Just missing some bad spots to guys you don't really want to miss to. Sometimes one or two pitches can really change an outing, especially as a reliever. That's why I don't think it really had anything to do with the shoulder."
A's manager Bob Melvin plans to ease O'Flaherty back into action before trying him out in a prominent role. He made two rehab appearances ahead of his return, allowing one unearned run over a combined two innings between Nashville and Class A Advanced Stockton.
"I felt good," O'Flaherty said. "I was in the zone, on top of the ball. Everything felt good and clean."
The A's could add a third left-hander to their relief mix as soon as Wednesday, when Drew Pomeranz (shoulder) is eligible to come off the DL. Though all eight of Pomeranz's appearances this year have been as a starter, he will pitch out of the bullpen upon his return, Melvin confirmed.
• Right-hander A.J. Griffin allowed just one hit and struck out three in three scoreless innings for Stockton on Tuesday night in his first rehab outing following Tommy John surgery.
Jane Lee is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.