Radke was released by the Padres on Tuesday, Jeff Sanders of The San Diego Union-Tribune reports.
The 27-year-old was added to the Friars' 60-player pool in early August, but he was unable to earn a major-league opportunity. Radke had a 2.97 ERA, 1.59 WHIP and 28:12 K:BB over 30.1 innings at Triple-A last season.