Nicasio is available out of the bullpen for Thursday's game against the Chicago Cubs.
Nicasio began the season on the opening day roster and was 5-5 with a 5.92 ERA in 14 starts. He was optioned to Colorado Springs on June 16.
Brown has had two stints the Rockies this season and made his major league debut July 6. He is 0-1 with a 6.75 ERA in 10 appearances with Colorado Springs.