Corpas, 31, made 224 appearances for the Rockies from 2006-10 before elbow surgery led to his departure. Corpas was 0-2 with a 5.01 ERA in 48 appearances with the Cubs last season. He rejoined the Rockies under a Minor League contract during the winter.
The club had also discussed promoting right-hander Chris Volstad, who began the season with the Rockies, and right-hander Logan Kensing, who pitched in the Majors with the Marlins and the Nationals, but were leaning heavily toward Corpas as of Saturday afternoon, according to a source.
In Corpas' first full season with the Rockies in 2007, he went 4-2 with a 2.08 ERA. He took over for Brian Fuentes as closer and earned 19 regular-season saves. He also earned two postseason saves.
Betancourt (1-3, 11-of-12 on save chances, 3.20 ERA) has chronic issues with scar tissue around the site of a 2009 right groin surgery. A major flare-up occurred May 21, when he had to be removed from an appearance against the D-backs. Betancourt has tried to pitch through pain since, but gave up runs in two of his three appearances, both losses.
The Rockies are likely to make left-hander Rex Brothers (1-0, 0.38 ERA, one save) the closer in Betancourt's absence.
Brothers' scoreless ninth inning in Saturday's 7-6, 10-inning victory against the Dodgers was his 23rd straight scoreless outing, spanning 21 1/3 innings.
Thomas Harding is a reporter for MLB.com. Ian McCue is an associate reporter for MLB.com. Read Harding's blog, Hardball in the Rockies, and follow him on Twitter @harding_at_mlb. This story was not subject to the approval of Major League Baseball or its clubs.