Triple-A Iowa placed Hollowell on its 7-day injured list April 12 due to an unspecified injury.
Hollowell possesses a spot on the Cubs' 40-man roster, but his injury will take him out of the running for a promotion to the big club anytime soon. The righty reliever made three appearances for Iowa prior to landing on the shelf, working 4.2 innings and striking out nine batters while allowing two earned runs on three hits and four walks.