Underwood (hamstring) was activated from the 10-day injured list Thursday.
Underwood has been sidelined since experiencing hamstring discomfort in the season opener, but he'll rejoin the active roster ahead of Thursday's matchup with the Reds. He had a 4.33 ERA, 1.43 WHIP and 65:27 K:BB across 72.2 innings for the Buccos last year.