Betancourt was 1-3 with a 3.20 ERA and 11 saves in 22 chances before straining his right groin on June 1. He has converted on 52 of 70 save chances since he was acquired from Cleveland on July 23, 2009.
Nicasio was 4-4 with a 5.31 ERA in 16 starts this season but has struggled lately. In his last start, at Boston on Tuesday, Nicasio allowed seven runs and 12 hits in 2 1/3 innings.
Rockies manager Walt Weiss said left-hander Drew Pomeranz will be recalled from Colorado Springs on Sunday to start against San Francisco.