Favre told Washington sports station WSPZ-AM he doesn't feel physically able to compete and expressed fear that he has been affected by concussions.
"It's flattering, but you know there's no way I'm going to do that," Favre said.
Fisher changed the subject after practice, then said "Nice try" when asked whether the 44-year-old Favre could be ready to play. Bradford is out for the season with a knee injury.
"I don't remember my daughter playing soccer, playing youth soccer, one summer," Favre told WSPZ. "I don't remember that. I got a pretty good memory, and I have a tendency like we all do to say, 'Where are my glasses?' and they're on your head. This was pretty shocking to me that I couldn't remember my daughter playing youth soccer, just one summer, I think. I remember her playing basketball, I remember her playing volleyball, so I kind of think maybe she only played a game or two. I think she played eight. So that's a little bit scary to me. For the first time in 44 years, that put a little fear in me. ...
"I think after 20 years, God only knows the toll."
Rams defensive end Robert Quinn didn't think there was anything to the reports.
"Brett Favre is staying retired," Quinn said. "Brett hasn't played since 2010 and he's comfortable down there in Mississippi on a boat or something. Have fun with it, Brett."
Kellen Clemens, the backup the past two seasons, will make his 13th career start Monday night against the Seattle Seahawks. The Rams also signed Brady Quinn and Austin Davis.
Fisher said he wouldn't discuss players contacted after Bradford tore his left ACL on Sunday at Carolina, although he confirmed Tyler Thigpen also worked out.
"I don't feel any need to disclose information after the process," Fisher said. "That's how we are. I'll be happy to talk about Thigpen, and the two that we signed."