"It's hard to map out," Weiss said. "We've got to build his arm back up. I'm not saying he's going to need as many starts as he would in Spring Training, but he's going to have to be built up a little bit."
Meanwhile, righty Tyler Chatwood, who felt tightness in the forearm after his live batting practice session on Tuesday, did not make the trip to Miller Park. The team said Chatwood was continuing his rehab with the club's trainers in Denver. Chatwood has been on the DL since April 30 with a right elbow strain.
Despite placing an emphasis on inducing ground balls at the beginning of the season, the Rockies had given up a Major League-high 100 home runs entering Friday, and Weiss said the absence of Anderson and Chatwood was a big factor in that.
"Fly balls usually do damage at our place, so the ability to get ground balls is important for everybody, especially for us," Weiss said. "Two of our big ground-ball guys have been out most of the year with Anderson and Chatwood. Regardless of who's out there, they've got to be able to find a way to execute that."
Caitlin Swieca is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.