Hollowell had his contract selected by the Rockies on Sunday.
Hollowell has been with Double-A Hartford all season and will now receive his first taste of the big leagues. The 24-year-old has appeared in 42 games for the Yard Goats this year and has a 3.14 ERA, 0.91 WHIP and 64:14 K:BB across 48.2 innings.