The Athletics selected Otanez's contract from Triple-A Las Vegas on Sunday.
Otanez has appeared in 22 games out of the Triple-A bullpen this season, posting a 3.99 ERA, 1.27 WHIP and 45:15 K:BB over 29.1 frames. He'll provide Oakland with right-handed depth out of the bullpen after southpaw Jack O'Loughlin was optioned to Triple-A Las Vegas in a corresponding move.