Manning will be called up from Triple-A Toledo to start Thursday's game against the Angels.
The 23-year-old was already listed as the probable starter for Thursday's contest, and he's now been added to the big-league roster. Manning has struggled at Triple-A this season with an 8.07 ERA, 1.56 WHIP and 36:10 K:BB across 32.1 innings, but he'll nonetheless receive the opportunity to illustrate why he's the organization's top pitching prospect.