Chacin is scheduled to start on Opening Day, April 1 at Milwaukee. Had he not suffered the back spasms on Thursday, he would have been asked to throw around 90 pitches on Friday. Instead, he worked two innings in an unfamiliar relief role Saturday in the Rockies' 10-4 victory over the Padres.
The two hits Chacin yielded were solo homers by Kyle Blanks and Cody Ransom. He left the mound with a 7.36 Cactus League ERA, with one start scheduled between now and the season opener.
"It was a little different for him, coming in, in the middle of the game," Weiss said. "It's not his routine.
"He got a ball out over the plate to a large man [Blanks], but I'm not too worried about him finding his way through lineups. He knows how to pitch."
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.