Underwood cleared waivers and accepted his outright assignment to Triple-A Indianapolis on Friday, Jason Mackey of the Pittsburgh Post-Gazette reports.
Underwood was designated for assignment last Saturday. The right-hander has produced an inflated 5.18 ERA and 1.44 WHIP with 14 punchouts over 24.1 innings in 20 appearances with the Pirates this season and will look to use his time with Indianapolis to reset after he allowed 10 earned runs over 10.2 innings in May.