When Bettis does return, potentially on Tuesday in Atlanta, Colorado could go to a six-man rotation to finish out the year.
"It's possible, certainly for the month of September," Weiss said. "We've discussed that. We're closing in on that, so we'll see. When all the pieces get healthy, we've got to unscramble them."
After shifting back and forth between starter and reliever until this season, Bettis said it would be "huge" to finish out the year strong as an integral member of the Rockies' rotation.
Before his injury, Bettis was 5-4 with a 4.88 ERA, having surrendered three earned runs or fewer in 10 of his 13 starts.
"It's huge," Bettis said of the season's final stretch. "One, to show that I'm healthy again. Two, to show that I didn't miss a beat. It's going to be big."
In addition to Bettis, the last six weeks will give the Rockies one final look at a number of rotation candidates moving forward. Veteran Jorge De La Rosa, who has one more year left on a two-year, $25 million deal, is set in stone, but there is much to be sorted out after that.
Inexperienced pitchers Chris Rusin, Jon Gray and David Hale will have a chance to prove themselves, while injured candidates Jordan Lyles (toe) and Tyler Chatwood (Tommy John surgery) wait in the wings.
Eddie Butler and Tyler Matzek, both currently in the Minor Leagues, haven't been forgotten as well, and Jeff Hoffman -- the key piece in the Troy Tulowitzki deal -- could also be up with Colorado in 2016.
"As a starting rotation, we have to understand and figure out how we all work best together, because we've got to keep moving forward," Bettis said. "We can't go backwards, especially now."
Weiss said Kyle Kendrick, who was sent to the DL with right shoulder inflammation on Aug. 1, will soon be facing hitters, possibly on Sunday.