Favre expects to play Monday night after the back of his head bounced off the Lambeau Field turf for a game-ending concussion on Sunday.
McNair, too, expects to play only two weeks after he was hospitalized with a bruised sternum, suffered in a loss to Jacksonville.
Favre was knocked from the Giants game after suffering the injury, trotted back onto the field moments later for a fourth-and-5 play, and threw a 28-yard touchdown pass.
McNair was injured while converting a third-and-10 into a first down with a daring scramble. McNair stayed in the game to complete the touchdown drive, then threw an incomplete pass on a two-point conversion try before being removed from the game. He wound up spending two nights in the hospital, then sat out Sunday's loss at San Diego.
McNair didn't think he'd practice Thursday, but did anyway.
"I went out there, played around, did some good things on the practice field. Did everything I possibly could do in a normal practice situation to see if I had any problem, and I didn't," McNair told Tennessee reporters after practice.
Favre practiced Thursday after being given Wednesday off to help clear the cobwebs from the concussion. Favre will practice Friday, then will return home to Mississippi to attend the funeral of his brother-in-law. Casey Tynes, 24, died Wednesday as the result of an all-terrain vehicle accident.
"Just coming off of a head injury and then, all of a sudden, he has this real heaviness on his heart, it's tough to see," offensive coordinator Tom Rossley said. "You could tell (at Thursday's practice) he wasn't himself. His mind was kind of elsewhere.
"But he'll rise somehow. We know he will."
The Titans expect the same from McNair. He's listed as questionable (50 percent chance of playing) on the injury report but has never not played in a game after practicing at least once in the days leading up to the contest.
"I'm going to play the way I usually play and as hard as I usually play," McNair said in a conference call with Wisconsin media before practice. "I just try and not think about it, and get the job done."
Like the Packers need Favre to play big, the Titans will demand the same of McNair. Both teams are 1-3, and only four teams in the long history of the NFL have qualified for the playoffs after starting the season 1-4.
"I think he'll be ready to take the team on his shoulders and get us out of this difficult situation," Titans coach Jeff Fisher said.