BALTIMORE -- The A's called on left-hander Brad Mills from Triple-A Nashville on Friday for a spot start against the Orioles, marking his first big league outing since July 1 of last year, and he responded with five innings in Oakland's 8-6, 13-inning loss.
Mills surrendered seven hits in that span, including a three-run home run to Adam Jones in the fifth inning, accounting for his only runs allowed in the 78-pitch outing.
He's expected to return to Nashville on Saturday, with the A's likely to bring in a fresh bullpen arm to take his roster spot.
"I felt all right," Mills said. "I wasn't sharp. I was behind in too many counts, but I felt I made pitches when I had to. You have to battle your way through games like that.
"I would've loved to at least get another inning or two, especially if you would've told me it would go extras like that. I felt like I gave it my best."
Adding Mills to the 40-man roster led the A's to designate right-hander Taylor Thompson for assignment. Right-hander Arnold Leon was optioned to Nashville to make room on the active roster.
Leon made just two appearances in his latest stint with the A's, allowing four runs on a grand slam in his first inning of work back with the club, before putting together two scoreless frames in his next outing.
"We probably really haven't given him enough outings to get a great handle on what he can do," A's manager Bob Melvin said. "I do think he has the ability to pitch well. He just needs a consistent workload to where he can prove that to himself. But each and every time he's here, he seems more comfortable on the mound to me."
The A's have 10 days to trade, release or pass Thompson through waivers. The right-hander spent much of the season recovering from a shoulder injury, returning from the disabled list just last week before joining Nashville.
Jane Lee is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.