Montana, at Pierce College filming a television commercial, said he believes it's only a matter of time before Favre returns to play for the Minnesota Vikings, the team he led to the NFC Championship Game last season.
Favre has remained undecided on his plans for the 2010 season.
"He says he's not sure [about playing] because he doesn't want to go to training camp. He's smart," Montana said. "I'm sure he already has that agreement with them. Nine chances out of 10 they already know and they've already had this whole conversation and they should just let everybody know because they know he's going to come back.
"He knows he's going to come back, but the reason they don't say anything is because he doesn't want to go through training camp," Montana said. "If he didn't have to go through training camp, his decision would already be made, but he should know by now going to training camp isn't going to be hard. They'd never make it hard on him."
Montana said Favre's familiarity with the offense and the talent around him will make the transition from Favre's couch in Kiln, Miss., to the football field seamless, even if Favre comes back in time for the final exhibition game.
"It's easy once you know an offense and have been there for so many years," Montana said. "All you really need is a couple quarters in a game and to get hit a couple times to get back in tune. You can get a lot of the other stuff in practices. It's just getting used to that movement and feel of the game. You can easily do it if you've played enough years."
While Montana, licking his fingers before firing spirals to extras on the set of a Skechers commercial, said he wishes he could still suit up on Sundays, he said he never considered a comeback after his retirement 15 years ago. He added that he always wished he could have played a couple of more seasons the way Favre has.
"Anyone who has played the game, once you get away from it, you always want to try and find a way to get back," Montana said. "You wish you were still playing but you know physically, unfortunately, it's impossible. I can run a 4.5 in the first 20 yards but that's it.
"I never even thought about coming back after I retired," he said. "I wished I would have stayed and played a year or two but once you get past that point and retire there was no way I could have done it."
Arash Markazi is a reporter and columnist for ESPNLosAngeles.com.