BALTIMORE -- The A's optioned right-hander Jesse Hahn to Triple-A Nashville on Sunday, a move prompted by the ramifications of Saturday's doubleheader in Baltimore.
The A's will need to call up another starter before Hahn pitches again, leading the team to send him out after just two starts; he pitched 6 2/3 scoreless innings against the Astros last week before allowing five runs (four earned) on Saturday night at Camden Yards.
"Threw us for a little loop, which happens over the course of the season, but timing probably not good for him," A's manager Bob Melvin said.
The A's recalled reliever J.B. Wendelken from Nashville to take Hahn's roster spot, giving them an extra arm for Sunday's series finale.

Wendelken, acquired from the White Sox in the Brett Lawrie deal this offseason, made his big league debut in the seventh inning of the club's 11-3 loss, giving up a leadoff single to his first batter, Adam Jones, before retiring each of his next three to end the frame. He quickly found trouble in the eighth, though, loading the bases and offering up a grand slam to Manny Machado without recording an out.
Wendelken came from Nashville with a 3.27 ERA in 10 games, carrying a 20-to-4 strikeout-to-walk ratio.
The A's are likely to call on lefty Eric Surkamp for one of the three starts in Boston. Melvin said rehabbing right-hander Henderson Alvarez is not an option. The plan remains for him to make at least two more Minor League rehab starts before joining Oakland's rotation.