The Rockies optioned Hollowell to Triple-A Albuquerque on Tuesday.
Hollowell made 26 relief appearances for the Rockies last season and had a 5.88 ERA, 1.46 WHIP and 32:18 K:BB across 33.2 innings. The 26-year-old struggled during spring training with seven runs allowed, including three homers, across 4.2 innings.