"Things are going well," manager Mike Quade said, "and I'm not interested in pulling the trigger on that. I'd like him to keep working there. I teased him yesterday and said, 'You never know, pal. Be ready.' We don't have the need that I thought we might when Derrek [Lee] left."
Lee was traded Aug. 18 to the Braves, leaving a gap, but Xavier Nady has handled first base, and the Cubs also called up Micah Hoffpauir.
Colvin hasn't played first base since his sophomore year in college, and it was only part-time then.
"It's going to be a new experience for him," Quade said of Colvin playing first. "I don't want him to show up tomorrow and, bang. Like I do with all of them, I want to give him a head's-up. Nady's making it tough for me to do that."