Francis, 32, the Rockies' No. 1 starter several years back, was 2-5 with a 6.58 ERA in 11 starts before being sent down to Triple-A Colorado Springs on June 20. At Colorado Springs, he is 2-2 with a 4.60 ERA in six starts.
The decision regarding Francis was first reported in a tweet by the Denver Post.
The move gives Francis a chance to shore up the Rockies' middle relief situation. With pitchers not going much over 100 pitches, the club needs solid relievers to protect leads or keep games tight for a solid late bullpen featuring right-hander Matt Belisle, left-hander Rex Brothers and right-handed closer Rafael Betancourt.
Righties Edgmer Escalona and Adam Ottavino and lefty Josh Outman have handled the role with varying degrees of success this year. Righty Wilton Lopez was expected to help in late innings but has struggled this year, and he is pitching in the middle innings but usually in low-leverage situations.
The move of Francis and the departure of Cook mean if the Rockies look to Colorado Springs for immediate rotation help, the possibilities are two recently acquired hurlers.
Righty Collin McHugh is a combined 4-3 with a 2.79 ERA with Triple-A Las Vegas and previously the Mets and Colorado Springs. Righty Armando Galarraga was 6-6 with a 2.98 ERA in 16 starts at Triple-A Louisville before the Rockies acquired him in a trade with the Reds on Monday. Galarraga will make his Colorado Springs debut Sunday.
Also, righty Chad Bettis, a second-round Draft pick in 2010 out of Texas Tech, has performed well in two of his three starts at Double-A Tulsa since returning from an oblique injury he sustained in early May.
Injuries have eliminated two other prospects who saw time with the Rockies last season from consideration this year.
Left-hander Christian Friedrich, who had some positive outings last year as a rookie (5-8, 6.17 ERA in 16 starts), has gone home to the Chicago area to rest after rehab exercises failed to work for a back injury. Friedrich, on Colorado Springs' disabled list, sustained a stress fracture in his lower back last season and experienced a relapse in Spring Training. The Rockies hope total rest, even if it costs Friedrich the season, will pull him past the problem.
Left-hander Edwar Cabrera, who went 0-2 with an 11.12 ERA last season but has not thrown a pitch this year outside of extended spring training, recently had surgery to clean out his left labrum.