The Rockies went 8-5 in Hanigan's starts between May 3 and when he was optioned on June 15, and he hit .264 with two home runs. Hanigan could have opted for free agency instead of going to the Minors, but said he liked the young, "hungry" Rockies team.
The Rockies have used as many as four rookies in their rotation at once.
"They don't act young, and the talent they have is far beyond their years, but now it's about getting outs in the big leagues," Hanigan said. "You can have talent and maturity and still not get outs. It's a tough game.
"It's about the little things. What can you do today that you didn't do yesterday? How can you get better? How are we going to face this team after we just faced them a week ago?"
The likely pattern is for Hanigan to start against left-handers -- he started Friday against the D-backs' Robbie Ray -- while lefty-hitting Tony Wolters (.288, .388 on-base percentage, .340 slugging percentage) will face mostly righties.
Murphy was 1-for-20 with a double, 11 strikeouts and an RBI in eight games after missing the first 2 1/2 months with fractures in his right forearm. Manager Bud Black said he and the staff thought Murphy was "pressing," and needed regular playing time in Triple-A.
To make room for Gray (0-0, 4.38 ERA), the Rockies designated righty reliever Chad Qualls (1-1, 5.40 ERA in 19 games) for assignment.
Thomas Harding has covered the Rockies since 2000, and for MLB.com since 2002. Follow him on Twitter @harding_at_mlb and like his Facebook page.
This story was not subject to the approval of Major League Baseball or its clubs.