Brad Johnson rose from ninth-round draft pick to Super Bowl champion because of intense competitiveness and a willingness to prepare.

He’s still got it. The former Viking can barely make it down a flight of stairs because of the beating he took as an NFL quarterback. A lack of mobility doesn’t keep him from preparing to win.

“We were playing George Walton,’’ Johnson said. “So I scouted George Walton 11 times.’’

He was referring to George Walton’s sixth-grade football team.

Johnson decided not to coach professionally, so he coaches his son’s teams in Georgia, and helps with the local JV and varsity basketball program.

“When I retired from playing, I decided I wanted to spend time with my family,” he said. “I couldn’t do that if I was coaching. But I can coach my boys’ teams.”

Johnson led three different franchises to the playoffs. He won a Super Bowl. Had he remained healthy in 1998, he might have led the Vikings to another Super Bowl.

New Vikings offensive coordinator Norv Turner has worked with blue-chip, first-round quarterbacks such as Troy Aikman and Philip Rivers. He also worked with Johnson, when the two led the Washington football team to the playoffs in 1999 — “last time they had made the playoffs, before 2012,’’ Johnson proudly notes.

As a quarterback who was both a long shot and a success, Johnson has a unique perspective on Turner.

“He’s one of my all-time favorites,” Johnson said. “He had an unbelievable feel for the game. More important than that, he had a great feel for people — who they were and how they functioned. He could find the strengths of each player.

“If there were certain throws I was good at, that’s what we did. If there were certain plays or reads I wasn’t good at, we discarded them. Washington, that year, had a great running game with Stephen Davis, so Norv built our offense off the play-action throw.”

Turner may be coaching a retread, a first-round draft pick or a lower-round pick next fall.

“He can work with anybody,” Johnson said. “It’s kind of like ‘The Horse Whisperer.’ Norv is the quarterback whisperer. There isn’t a play he hasn’t seen or a throw he hasn’t seen. He’s had great success and his systems carry over from one player to the next.”

Johnson played from 1992 through 2008.

“The game has evolved incredibly,” he said. “When I first got into the league, you could read only one side of the field. Then it got to a point where you could read the whole field, with different progressions.

“Then you would call two plays in the huddle. Then you’d call a run and a pass in the huddle. Then we used shifts and motions. Now the defenses are making checks at the line. Now you have both sides making fake checks.

“The game is so fast now. It’s incredible to me how good these quarterbacks are.”

Watching and coaching his sons has given Johnson insights into why someone like Russell Wilson can succeed so quickly in such a complex league.

“When I watch my kids play video games, they’re calling real plays against real coverages,’’ he said. “Kids are learning at such a faster pace. Guys are throwing for 5,000 yards now. You couldn’t do that 15 years ago. The rules would not allow it. The offenses wouldn’t allow that.

“Now, you’d better learn at a young age if you want to advance to the next level. My kids can draw up a corner blitz, a Mike-Sam blitz, and they’re 10 years old. They can tell you, in a one-back set, whether the play is going to be a run or a pass by the depth of the back in the formation.

“In the youth coaching I do, we have kids out here in their full pads on July 10. It’s ridiculous. The colleges and pros haven’t even started camp yet. But that’s how these kids improve so much.”

Turner could wind up coaching someone like a young Johnson — a talented long shot. Or Turner could wind up coaching someone like an older Johnson, an experienced quarterback passed over by other teams.

Either way, Johnson endorses the Vikings’ new offensive coordinator.

“I wish I had had more time with Norv,’’ Johnson said. “He helped my career. He helped me learn how to make proper reads, how to make the right throws. To have that kind of relationship with a coach, that’s what ever player wants.”