Of the 90-plus players on the training camp roster, perhaps no player faces longer odds at making the final roster than McBrien, an undrafted rookie.
It's not that McBrien is a bad player. The left-hander started two seasons at Maryland, completing 55.1 percent of his passes during his senior campaign for 2,672 yards and an outstanding touchdown-to-interception ratio of 19 to 6.
But in a league starved of quarterback depth, the Packers enjoy an embarrassment of riches. Favre is a certain Hall of Famer. Couch is the former No. 1 pick in the draft who has looked every bit that resume at times during training camp. Doug Pederson is the smart veteran who may not win a game but certainly won't lose one. Third-year player Craig Nall is in a fight to make the final roster, but if he's released he'll surely be picked up quickly by another team.
That leaves McBrien as the fifth of five quarterbacks. That means only a trivial number of snaps in team situations at practice, unless the stars aligned like Friday afternoon when Nall, Couch and Favre watched from the sideline.
"It was good to get in there and get a lot of repetitions," McBrien said. "That's what it's going to take for me to get comfortable."
He may not be comfortable yet, but compared to veteran Akili Smith last season, McBrien looks remarkably poised. He throws it well on the run and is athletic. He's listed at 6 foot on the roster, but that's only on his tippy toes, so he's not exactly the prototpye NFL quarterback.
As is the case with most rookies, especially at quarterback, the learning curve is steep simply because the West Coast offense is so much more complicated than what he operated under at Maryland.
"It's pretty tough. New terminology, of course, is always tough," he said. "Just getting into your playbook is the main thing. For me, it's my job to go back in my room at night and really study. I can't go to bed at an early hour. I've got to be up studying. Hopefully it's going to pay off someday."
Facing such a talented foursome of quarterbacks, it would be easy for McBrien to get down on himself or to chalk up this training camp as being in the right place but at the wrong time. Instead, McBrien looks at his circumstances with optimism.
"It's an advantage for me. That might sound weird. But it's an advantage for me because I get to sit back and watch them work and watch them operate and really learn from them," McBrien said.
"When I'm given the opportunity, it's my turn to step up and take what I've learned from them and carry that over on the field. I'm just blessed to be here and be around such a great group of guys and great staff and great tradition and a great program."
While Favre is getting ready for the season, Couch is trying to learn the system and Pederson and Nall theoretically battle for the final quarterback spot on the roster, it would be easy for McBrien to get lost in the shuffle. Instead, he says his teammates have been offering advice and answering questions.
"They're helping me out every day," he said. "They know I could be in a situation where I'm going to have to play. Whether it would be a preseason game or here in practice or whatever, they're here to help me out. I'm thankful for that. They don't have to do that. That just shows you what great guys I'm around."
McBrien looks forward to Saturday's scrimmage with optimism. Nall is out with a hamstring injury, but Couch's sore arm should be healed from a day of rest. The Packers need to get Favre ready for the season, and Pederson will get his reps, too. That leaves McBrien unsure of how many snaps he'll get on Saturday. He says he'll be ready to perform, regardless of how many chances he gets.
"It's my job to just take everything and the opportunities I'm given and hope things work out," he said.
A year ago, Eric Crouch was fifth on the quarterback depth chart, saw no hope of making the team, and quit. Don't look for McBrien to do the same thing.
"My goal is to try and make this team. I'm not going to quit. I'm not a quitter," McBrien firmly said. "I'm going to try to make this team, and if I don't, my goal is to take what I've learned from this experience and from Brett and the other quarterbacks and carry that over to somewhere else. If it doesn't work out it doesn't work out, but I'm just thankful to have this opportunity."