"I don't want to commit to that right now, but I think it would probably be tough to make his next start, if he misses bullpens," Rockies manager Walt Weiss said. "We want to make sure that the next time we run him out there, he's right."
The Rockies removed Chatwood after he tossed four innings on Monday, and Chatwood said after the game he felt the injury during the third inning, and after that struggled when he tried to throw to his glove-side.
A preliminary evaluation by Rockies medical director Dr. Thomas J. Noonan found no structural damage, and he ordered the precautionary MRI. Chatwood flew to Denver on Tuesday for the test.
"I don't think it's bad," Rockies head athletic trainer Keith Dugger said. "He overextended on a pitch, kind of pinched the back of his elbow, kind of inflamed the triceps tendon a little bit. We were over-cautious and got him out of the game.
"He felt good, talking to him, and he didn't report any unusual soreness."
The Rockies will re-examine Chatwood Thursday, after they return from their current road trip.
Colorado has been cautious with injuries throughout the season. Weiss declined to speculate about the identity of the starter Saturday against the Padres at Coors Field.
Thomas Harding is a reporter for MLB.com. Read his blog, Hardball in the Rockies, and follow him on Twitter @harding_at_mlb. This story was not subject to the approval of Major League Baseball or its clubs.