Underwood (hamstring) threw a side session Monday and is expected to join the Pirates for their weekend road trip in Chicago to face hitters in live batting practice, Jason Mackey of the Pittsburgh Post-Gazette reports.
Pitching in the live batting practice will likely be the final hurdle Underwood needs to clear in his recovery from a sore right hamstring before the Pirates send him out on a minor-league rehab assignment. As a reliever, Underwood won't require much ramp-up time, so he could be ready to return from the 10-day injured list before the end of April or in the first week of May.