Whitley was outrighted to Triple-A Gwinnett on Saturday.
Whitley has appeared in two games for the Stripers in 2018, tossing 13 innings and allowing four runs while fanning 14. The 29-year-old was called up to the big leagues for a brief stint with the Braves in April, but he was sent down after surrendering two runs over one inning out of the bullpen.