Still, some people, mostly old people, think he's too young for that job.
He's not. He's not an idiot. If he ever was an idiot, it lasted for about 10 minutes, and then he moved on to the business of growing up. He's forever been grown up. He's an old man in a young man's body, one of those rare individuals who always bought his cereal for the fiber, not the toy, a kid wise beyond his peers.
"I've always been young for everything I've done in my life," he said. "It's never bothered me one bit."
And it doesn't bother him now.
Check out Johnson at the practice field on Saturday. He didn't raise his voice. Didn't look flustered. He just moved from drill to drill, seamlessly and confidently, the master at the helm of his offense.
Yes, it is only March. But Johnson has seen his share of Septembers, Octobers, Novembers past, for a time as an assistant coach and longer as a quarterback.
"We've got a ways to go, but I feel comfortable with the attention to detail and the focus of our players," he said. "We've got a lot of guys who have played here. They know what the expectations are."
Expectations set, in part, by Johnson himself.
It's a combination of that playing experience with the nature of the man that indicates likely success for him as he works his way through the vicissitudes of coordinating the Ute offense.
Johnson arrived at Utah at the age of 17. He was Alex Smith's backup as a freshman, and then moved to the starter's spot. He waded through good and bad times, and after multiple injuries returned to lead the Utes to their pinnacle in 2008, going undefeated and winning the Sugar Bowl.
A few quotes and anecdotes stand out as illustrative from that season, one from the comeback win against Oregon State and the others from the moments after the win over Alabama.
Against the Beavers, when Utah trailed by eight points with less than two minutes left, Johnson saw fans filing out of Rice-Eccles Stadium. He said to teammates: "They're going to miss a great show."
After the Utes' win in the Sugar Bowl, as the confetti fell on his head, Johnson said: "Nobody believed we could do this … except for us. And we did."
Minutes later, Louie Sakoda said of Johnson: "All of America doubted him. But his leadership made this team this year."
My personal favorite Johnson story occurred about an hour after that, when the quarterback walked out of the Superdome with his backpack in one hand and the MVP trophy in the other. He looked around and saw nothing but darkness and an empty road running off into the distance.
It was 1 a.m. and he was alone.
Ninety minutes after the biggest win in school history, team busses somehow had left their MVP behind. Under the brightest lights, he had thrown for 336 yards and three touchdowns against Alabama.
And now, he was forgotten.
With a disheveled street person closing in, Johnson audiblized, and with more panic than ego, punched up Whittingham on his cell phone and said: "Where is everybody? Why did you leave me?"
The voice responded: "We did?"
Whittingham's never forgotten Johnson since.
He first hired him as a quarterbacks coach and then, when Norm Chow bounced for Hawaii, Whittingham replaced one of the oldest offensive coordinators in the land with the youngest, recognizing Johnson's advanced maturity, his brains and diligence and his calm-but-charismatic demeanor.
Not only had the new OC absorbed and understood Utah's playbook as a quarterback, often calling the plays himself, he also spent hours in the film room. Last season, he came to work early and left late, frequently after more senior assistants had cleared out.
If Johnson grasps offensive concepts and has a strong work ethic, if he knows how to coolly call plays, and he has the personal wherewithal to inspire others "Everyone fed off his energy," Sakoda said what difference does it make whether he's 25 or 55?
It doesn't because … he's not an idiot.
The offense Johnson is installing is a pro-style hybrid, but he hesitates to label it as anything specific. "I don't have a magic word for it," he said. "It definitely will be diverse."
Johnson has consulted with people he trusts, including Dan Mullen and Smith, and said he's continually taking in new information. He admits he's still learning. But his old soul and young mind are a good mix.
It was Satchel Paige who once asked: "How old would you be if you didn't know how old you were?"
Brian Johnson is that age.
"I'm ready for this," he said. "No doubt in my mind, I'm ready. We can't wait to get this thing going."
GORDON MONSON hosts "The Gordon Monson Show" weekdays from 2-6 p.m. on 97.5 FM/1280 AM The Zone.