Underwood is active with High-A Myrtle Beach after rehabbing an undisclosed injury with the AZL Cubs in August.
Underwood started a game for Myrtle Beach earlier this month, allowing one run on three hits with zero walks and two strikeouts over 4.2 innings, as he is apparently over the undisclosed ailment that kept him sidelined for almost all of July and half of August. Underwood's prospect stock has taken a hit with concerns about his workload, his ability to throw strikes, and his strikeout potential. He'll likely begin 2017 with Double-A Tennessee, aiming to improve upon the 4.91 ERA, 1.65 WHIP and 46:31 K:BB he posted in 58.2 innings with that affiliate this season.