DENVER -- Rockies manager Jim Tracy announced before Sunday's game against the Cubs that staff ace Aaron Cook's next start will be pushed back.
Cook was slated to start Tuesday against the Pirates but will now pitch on Saturday against the Marlins.
The right-hander suffered a hyperextension of the right big toe in Thursday's 3-1 loss to the Phillies when he was backing up third base on a Jimmy Rollins triple in the fifth inning. Cook said the toe began to irritate him in New York, which was the first stop during the Rockies' recent 10-game road trip.
Cook said he feels discomfort when his right foot is pushing off the pitching rubber. He will see a foot specialist Monday.
"As you're pushing off, it's just in that joint in the big toe," Cook said. "It makes it tough to push."
The club is approaching Cook's injury with caution, similar to the way it handled Jason Marquis' blister on the middle finger of his throwing hand. Last month, Marquis went nine days between starts so new skin could grow on the injured finger.
Tracy said the leading candidates to make a spot start Tuesday are veteran Josh Fogg and youngster Jhoulys Chacin. Tracy won't make a decision yet because he wants to see how starters Jason Hammel and Jorge De La Rosa fare on Sunday and Monday. Fogg is Tracy's preference for Tuesday's start.
"If we were to stay away from Fogg [in the bullpen and] we get a short start from one of our starters over the course of the next couple of days and avoid him because we want to push the envelope and have him start the game on Tuesday," Tracy said, "then you run into [Rafael] Betancourt and [Matt] Daley and Franklin Morales pitching innings where it makes no sense for them to be out there."
Tracy said Franklin Morales, who was a starter but returned to the team as a reliever on July 6 after a rehab stint in the Minors following a left shoulder strain, will not be considered.
"Franklin has pretty much pitched enough now in the role we have him in to where his arm is conditioned for that," Tracy said. "That's not to sit here and say that you couldn't run him out there. But it's going to be a much shorter outing and if it is, you're running the risk of waiting in the territory where you got to fill innings with guys that would make you very uncomfortable doing that with. I'm not willing to take that gamble."
Cheng Sio is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.