Underwood could start for the Cubs on Monday against the Reds, Sahadev Sharma of The Athletic Chicago reports.
The Cubs may need a spot start after Tyler Chatwood missed his start Sunday with his wife in labor. Underwood would be a logical option as he'd be lined up to start that day and is already on the 40-man roster. He has a mediocre 4.27 ERA in 71.2 innings for Triple-A Iowa so far this season.