Cook (10-4, 3.93 ERA) was supposed to start Tuesday against the Pirates, but a hyperextension of the big toe on his right foot forced manager Jim Tracy to postpone that start. Cook visited a specialist on Monday to make sure there was not a more extensive injury, Rockies head athletic trainer Keith Dugger said.
The start was delayed so Cook wouldn't risk changing his motion, which could put him in danger of injury. Tracy announced after Monday's 11-5 win that right-hander Jhoulys Chacin (0-0, 1.80 ERA) would take the mound on Tuesday, instead of right-hander Josh Fogg (0-1, 2.17 ERA), as was previously expected.
Cook is expected to throw a bullpen session on Thursday.
In other injury updates:
Right-handed reliever Manuel Corpas, who underwent arthroscopic surgery to remove a bone chip from his throwing elbow, will play catch on Tuesday or Wednesday.
Left-hander Alan Embree, hoping to return by the end of the season from his fractured right tibia (suffered when he was hit with a line drive on July 10), is playing catch, but the Rockies are exercising extreme caution.
"He's just doing light toss," Dugger said. "He can't really shift weight on it. He's walking. We're going to be smart. We're not going to push too hard. We can't take that chance."
Dugger said a follow-up X-ray is planned in the next couple of days.
Right-hander Greg Reynolds, the Rockies' top pick in the 2006 First-Year Player Draft, has spent much of this season on the Triple-A Colorado Springs disabled list because of a problem in the shoulder blade area. Now, Reynolds is trying to rebuild his motion from scratch.
The problem, Dugger said, was Reynolds changed the start of his delivery at one point, but it led to him squeezing the back muscles together. That led to the injury, and he'll have to break the habit before returning to the mound.
Lefty Greg Smith, who has spent much of this year at Colorado Springs disabled with a shoulder injury, is throwing bullpen sessions.
Thomas Harding is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.