The Red Sox designated Kahnle for assignment following Tuesday's loss to the Nationals, Chris Cotillo of MassLive.com reports.
The decision to remove Kahnle from the 40-man roster comes shortly after he gave up four earned runs on four hits and a walk in the eighth inning of Tuesday's contest, giving the righty an 8.00 ERA and 2.00 WHIP through nine innings on the year. Alec Gamboa is expected to be recalled from Triple-A Worcester on Wednesday to claim the vacant bullpen spot.