"We may have a hard time working that in," Roenicke said. "We'll know a lot more in the next couple of days. What we kind of thought may happen probably won't, so we'll go on a new plan of action.
"I should know in a couple days. Maybe by tomorrow I'll get a better idea."
Nelson, the Brewers' top prospect according to MLB.com, will remain in the bullpen, where the right-hander has pitched five scoreless innings since his September call-up from Triple-A Nashville.
Roenicke said he is not concerned with the amount of time since Nelson's last start, which was on Aug. 31 with Nashville.
"Not so much that because we got him two innings [on Wednesday against the Cubs]," Roenicke said. "We want to get him some innings, so whether it's out of the bullpen or whether it's starting a game, I would like to see him out there. If we can get him three, four more innings, I think that'd be great."
Kevin Massoth is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.