It was a risky signing for a reliever recovering from Tommy John surgery, and O'Flaherty didn't make his A's debut until July of last year, returning to the mound to post a 2.25 ERA in 21 games. He was expected to post similar numbers in a setup role this year, but he was sidelined for a month with a left shoulder strain and never really got back on track.
The A's used his roster spot for Saturday starter Aaron Brooks, acquired this week in a deal with the Royals for Ben Zobrist.
"It's not uncommon after Tommy John that it takes a while, some guys more than others," A's manager Bob Melvin said.