Kahnle was optioned to Triple-A Charlotte on Tuesday, the Chicago Tribune reports.
Following an offseason trade from the Rockies, Kahnle was in play for a bullpen spot with the White Sox, but his fate was sealed by a poor spring performance that saw his ERA sit at 7.00 through seven appearances. The 26-year-old will start the year back in the minors, but it's possible he'll see some time in the big leagues should they find themselves in need of extra arms.