De Leon was acquired by the Reds from the Rays on Wednesday for cash and a player to be named later.
De Leon spent most of the season at Triple-A Durham, but he did have seven strikeouts with one runs allowed over four frames with the Rays. The 27-year-old made 13 starts at Triple-A and had a 3.51 ERA, 1.33 WHIP and 73:27 K:BB across 51.1 innings, though he's more likely to serve as a multi-inning reliever in the majors.