Then he wasn't drafted.
Then he joined a UFL team that went out of business.
Then he signed with the Philadelphia Eagles.
Then he was cut.
All of this happened in the space of 10 months, or probably about 13 months if you include the complete fall from preseason Heisman hopeful to out-of-work athlete.
But Johnson didn't give up on his dream. He signed with the Steelers, and a year after being cut by the Eagles Johnson's in line to play as much as the three other Steelers quarterbacks combined at the halfway point of the preseason.
Who is this guy? And why is he going to play so much again Sunday night?
"He's a guy that hasn't had a bunch of in-game experience, particularly prior to this year," Steelers coach Mike Tomlin said in preparation for Sunday night's game against the Indianapolis Colts.
"Even though he's been in an NFL training camp, I think he's only taken about four preseason snaps. We want to see what he is capable of. We want him to get acclimated to an environment and give him a fair opportunity to see what he's capable of."
In the second half last week, Johnson threw only one impressive pass, a back-shoulder out to Tyler Beiler for 30 yards that set up a go-head field goal right after the two-minute warning.
Throughout the remainder of the game, Johnson completed 2 of 5 passes for 93 yards, including a screen pass to Chris Rainey that went 57 yards for a touchdown.
Most of Johnson's incompletions that night were similar to his camp incompletions: butt ugly.
Still, Tomlin wants to see more.
"He's a young guy that's showing the growth and development that young guys show," Tomlin said. "He's had some good days and he's had some days where he's taken a step back or two."
Tomlin said that "we're looking at four candidates probably for three spots," so he doesn't want to make a mistake on Johnson, an imposing 6-foot-5, 251-pounder with exceptional mobility and a work ethic and personality that had Tomlin raving the first night of training camp.
Johnson was a highly regarded pro prospect before undergoing shoulder surgery in the spring of his senior season. He may have come back too soon because he lost velocity and accuracy, and he's struggled with the latter at this camp.
But Tomlin refuses to give up on him, probably because he saw Johnson play on a Thanksgiving night in 2009 when the college football world watched open-mouthed at the athletic show put on my both Johnson and Colt McCoy.
Johnson passed for 342 yards and rushed for 97. McCoy passed for 304 and rushed for 175 in Texas' 49-39 win. It set McCoy up to be drafted the following April, but Johnson – a coach's son and dedicated Aggie – opted to return for his senior season. It may have been his undoing.
"After that game was the first time my shoulder started to hurt a little bit," Johnson said Friday at St. Vincent College. "I had surgery on my rotator cuff that January. I rehabbed and came back my senior year and it just got sore again. I just wasn't the same."
Johnson said he fell for the preseason hype and "I worked a little bit too hard in the offseason. Once the season got there, it kind of gave out on me."
Part of Tomlin's patience in Johnson has to do with the fact Johnson took five months off after being cut by the Eagles to let his shoulder heal. Tomlin also wants to see what can happen if Johnson re-locates a consistent release point in his throwing motion.
"My shoulder hurt for so long and my throwing motion had become how it was when I was hurt," Johnson said. "I got that time off to really kind of grind out how I was going to throw the ball and I got my throwing motion set now and I'm having the success I'm used to having."
And so he's being called upon to play the second half once again.
He was asked if this is his Super Bowl.
"Absolutely," he said. "Those other guys have played so much football, man, and they've had great careers and they're veterans, so our preseason minds are probably a little bit different. This is my opportunity to play. Any time I step on the field, especially in a game, I take it seriously. Hopefully it can be a breakout game for me. I'm going to go out there with confidence and guns blazing and try to put some points on the board."
It's been a rough couple of years for a player with loads of upside potential. Tomlin knows this and is willing to give him every last opportunity. It's what coaches with patient bosses in stable organizations are afforded to do.
"He's sharp, he's attentive, he has the desire to be great, and he's working extremely hard," Tomlin said.
At least Jerrod Johnson will make the second half of the second preseason game worth watching. He has that kind of upside. And he's the kind of person you root for.