The decision was made after a messy start Wednesday at Class A Short-Season Boise, when Matzek walked five and hit a batter -- and all scored -- at Eugene. It was the latest mishap in a year that saw Matzek begin in the big league rotation but pitch himself out of a job and see matters worsen in the Minors. There is no schedule for his return.
Matzek, 24, the team's top pick in the 2009 Draft out of Capistrano Valley High in Mission Viejo, Calif., was 2-1 with a 4.09 ERA in five starts for the Rockies, but was optioned to the Minors in May after he walked 19 in 22 innings. After he walked seven and yielded one hit in his first start at Triple-A Albuquerque, Matzek was removed from competition to rebuild his motion in hopes of finding consistency.
He had one outing in extended spring action against a Giants club during which he had good and shaky sequences, then made three appearances for Boise. The first two were scoreless, one-inning outings, then Wednesday's spun out of control quickly.
"We're working to get him to where the mechanical part of his game and the mental part of his game are working together," said Wiley, a former Major League pitching coach, personnel director and scout who took over the development of the Rockies' pitchers in 2013. "I've had other guys in the past that we've done the same thing with. Sometimes you put so much on yourself because you're working so hard to come back that you need to get away."
Matzek asked for and received a break in 2011 while in Class A ball, and built himself to Major League level from there.
Asked if Matzek can shake the issues and eventually return to the Majors this season, Wiley said, "Who knows? It just depends on how the process goes. We hope so."
Manager Walt Weiss expressed confidence that Matzek, Wiley and organization coaches such as roving pitching coordinator Doug Linton will find the right combination.
"We still believe he's going to be a top-of-the-rotation-type guy, and we're trying to get him back here," Weiss said.
Thomas Harding is a reporter for MLB.com. 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.