The Cubs optioned Underwood to Triple-A Iowa on Saturday, Jordan Bastian of MLB.com reports.
Underwood was one of three pitchers optioned to the minors and 15 players dismissed from big-league camp as the Cubs pared down their spring roster with Opening Day less than two weeks away. The 2012 second-round pick received his first cup of coffee with the Cubs last season, tossing four innings of one-run ball in a June 26 spot start. He'll likely fill a spot in the Iowa rotation.