Kahnle was optioned to Triple-A Scranton/Wilkes-Barre on Monday.
Kahnle has struggled mightily for the Yankees this season, compiling an unsightly 7.00 ERA, 1.78 WHIP and 10.0 BB/9 across nine innings, so he'll head back to the minors to clear his head and work some kinks out. Adam Warren, who was activated from the disabled list in a corresponding roster move, will take his place in the bullpen and on the active roster. Kahnle owns an impressive 2.60 ERA and 12.1 K/9 over 90 innings the past two seasons, so he should be back with the big club after he gets back on track with the RailRiders.