Bobby Ramsay knew Derrick Henry would be an NFL player as a 14-year-old at Yulee High School in Florida. By Henry’s senior year, the Yulee coaching staff jokingly gave up game planning from week-to-week because of the crazy variations opponents would concoct in attempt to slow Henry down. Once, Yulee faced a 6-5 base defense.

Didn’t matter. Henry ran for a 12,124 yards, a national high school record, during his Yulee career. He rushed for 4,261 yards as a senior.

“He’s the best running back in the history of high school football,” 247Sports National Recruiting Analyst Charles Power said.

247Sports National Recruiting Director Steve Wiltfong calls Henry the best high school football player ever.

That prowess transitioned to college. Henry won a Heisman Trophy at Alabama in 2015. He’s dominated in the NFL, too. Henry led the league in rushing yards and touchdowns this past season, quite literally carrying Tennessee to the AFC Championship game Sunday in Kansas City (3:05 p.m. ET, CBS).

Henry is a freak in every sense. He’s 6-foot-3, 247 pounds and runs a 4.5-second 40-yard dash. The dominance of the No. 12 overall player in the 2013 247Sports Composite should be expected at this point. Yet … the chip on Henry’s shoulder sits rigid. Yes, it’s the ultimate sports cliché. You’re probably wondering: How does this all-time high school player even have doubters?

Turns out teams once thought Henry was too big and too fast to play running back.

“(Derrick) was sitting there going, ‘I’d love to play running back, just give me a chance,’” Ramsay said.

Pause for a second and consider the hilarity that is a record-setting high school running back – Zeus vs. Boys in Florida high school football – politely asking college programs for just an opportunity to begin his career at running back.

Ramsay gets worked up about it to this day. His voice rises a little at the absurdity it all. Terry Richardson, then the running backs coach at Miami, visited Yulee High School to recruit Henry. Watching the tape for a minute he turned to Ramsay and said, “I just don’t see it.”

“Then he gave me this, you’re-an-idiot look when I said he’d play running back,” Ramsay said. “You don’t want to get into it with those guys yelling and screaming. But it’s like: ‘You know what man, maybe this is why you got fired.’ Maybe if you took him as a running back, he would’ve been interested in wanting to come there.”

Florida did much the same. Henry grew up a Gators fan, worshiping at the altar of Tim Tebow. Ramsay thought Florida could get back in the mix when Henry decommitted from Georgia in the summer prior to his senior year. One of Florida’s coaches told Ramsay: “I’m not sure if he’s an offensive player.”

Recruiting analysts doubted Henry, too. Ramsay remembers a conference call with ESPN prior to a national televised game Henry’s senior year. As Ramsay remembers, ESPN recruiting analyst Tom Luginbill said at one point during the call, “You know he’s not going to play running back. Come on man.”

“I think to this day if Derrick saw Luginbill, he’d probably try to fight him,” Ramsay said.

It’s not as if doubt stopped trailing Henry once he won a Heisman Trophy. Henry tested out of this world at the NFL combine. He paired massive size with 4.53-second 40-yard dash speed and a 37-inch vertical. The problem was his 20-yard shuttle, which clocked in at 4.38 seconds. That’s slightly below average for a running back, indicating potential issues with change of direction and suddenness in the hole. Again, people thought he was too big.

Henry dropped to the second round. In rookie minicamp he stumbled over a bag in a drill, leading to this headline from For The Win: “Derrick Henry’s Footwork Looks Awful.”

“He’s always had that chip on his shoulder,” Ramsay said. “I think it’s something that still bothers him.”

Henry used to watch highlights of bigger running backs like Eric Dickerson and Marcus Dupree, looking for any edge or styling that would convince the world he could play running back. It probably didn’t help Henry that his upright running style, a form that looks more sprinter than running back, worried teams because it increased a defender’s already wide strike zone.

Still, the doubts largely came down to one thing: A lack of imagination.

“There wasn’t really a lot to question,” Power said. “It was just that he didn’t really look like a running back.”

Ramsay used to tell coaches Henry is a speed guy. People see his size and assume Henry should function as a battering ram. But Henry wanted to get out in the open field. How else would he average 9.2 yards per carry as a senior?

Henry had an NFL-best 99-yard touchdown run in 2018. He’s had runs of 68, 74, 53 and 66 yards since the start of November, helping the Titans win seven of the last eight games he’s played in. Henry’s been responsible for 69 percent of Tennessee’s offensive production since the start of the postseason.

He’s both tank and home-run threat, an old-school running back so feared that eight-man boxes are doing nothing to slow down the entirely predictable. He’s making NFL stars look like the high school players of yesteryear that used to bounce off Henry like a pinball.

“Watching high school players trying to tackle this guy was a mind-altering experience,” Power said.

Even Henry’s jump pass last week isn’t a surprise. Henry would line up as Yulee’s wildcat quarterback 25 percent of the time late in his high school career. His arm is so strong that he served as Yulee’s Hail Mary passer if the situation called for it.

Nashville has dubbed Henry “King” during this playoff run, appropriate given that he’s an athletic marvel akin to LeBron James. But unlike some other players of Henry’s stature, Henry’s long had to stiff-arm away the doubters that questioned his very football identity.

Ramsay talks about Henry multiple times a day. He knows what motivates his former pupil. He also knows that Henry’s play has removed any remaining oxygen from a debate that’s lasted years.

“There was a lot of that in high school and coming into the NFL,” Ramsay said. “I think people have finally given up.”