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 start since July 1 of last year.
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.
Mills has spent the entire season with the Sounds, pitching to a 4-11 record and 4.45 ERA in 22 starts.
"He's been pretty consistent for them this year," A's manager Bob Melvin said, "and he does have a little bit of history against this team.