The Athletics optioned O'Loughlin to Triple-A Las Vegas on Sunday.
Though he was called up from Las Vegas on June 25, O'Loughlin went unused out of the bullpen until the Athletics' 19-8 win over the Orioles on Saturday, when he gave up five runs on seven hits and two walks over 2.2 innings while mopping up. The Athletics activated Kyle Muller (shoulder) from the 15-day injured list to replace O'Loughlin in the bullpen.