Chacin becomes the sixth starter out of commission for the Rockies. The team has already used 12 different starters this season.
The move is retroactive to Sunday.
Chacin missed the first month of the season with a strained right shoulder. He's 1-7 with a 5.40 ERA this season.
Bettis is 0-1 with a 10.05 ERA in 13 games with the Rockies this season.