The lesson came with unexpected force, enough that you might understand if Toby Gerhart didn't remember it. Or, at the very least, had tried to forget it.
But he does remember.
Last summer, at his first NFL training camp practice, he learned the difference between college and the pros.
Practice was in shells -- helmet and shoulder pads. Gerhart ran out of the backfield, caught a screen pass. Enter defensive tackle Pat Williams.
"I turned and he just de-cleated me," Gerhart said after Monday's Vikings practice at Winter Park. He was smiling at the memory. Really. "I was like, 'We're not even in full pads.' It was ... I didn't know what to expect."
Now, he does. And that is making all the difference as Gerhart tries to carve out a larger role as the backup to star running back Adrian Peterson.
A season ago Gerhart came out of Stanford as a second-round draft pick with gaudy numbers and a reputation for being a power runner. For the first weeks of training camp, the veterans made sure he paid his dues. Williams clobbered him early and often, then talked at length about it. This wasn't college anymore, he said. Time to test the college kid. There was a scuffle with defensive end Ray Edwards. At times it looked as if Gerhart had a horn on his helmet and a target on his back.
Gerhart holds no nostalgia for that camp. Nor does he have any lasting bruises, either literal or figurative. But he will tell you that going through it all made him stronger.
"I was known for being a power runner, and I got tested, early and often, in training camp," he said. "There were dues to be paid, evidently. And I feel I grew from that."
A year ago, by his own admission, Gerhart was a bit tentative, perhaps slowed by the thought process of becoming an NFL back. He recalls obsessing about his footwork, every little detail. He remembers counting his steps while running routes. "I was being really robotic," he said. "You know, one, two, counting my steps rather than just playing football like I've always done."
This time, Gerhart said, it's different. He says he's more relaxed, confident.
Will that translate into more opportunity? It always will be difficult playing behind Peterson. And while the previous coaching regime might have groomed Gerhart as a third-down back, he appears to be penciled in as Peterson's power-running backup. Indeed, Lorenzo Booker could emerge as a third-down option.
Still, with offensive coordinator Bill Musgrave's dedication to the run, there should be opportunity. Gerhart also could see some snaps while on the field with Peterson. It's up to Gerhart to prove he's ready.
"Toby came back in much better shape than his rookie year, when he wasn't sure what NFL football was like," Vikings coach Leslie Frazier said. "He's running with great authority. He reminds you much more now of what he did in college, the way he attacks the hole. He has a real good run in [Saturday's game, a 9-yarder]. We have high hopes for Toby really being able to help us in that backup role."
That might be why Gerhart is more relaxed and more confident. Having already paid his dues helps, too.
"It was about stepping in there, keeping your mouth shut and playing," linebacker Chad Greenway said. "He did that very well. ... We've seen marked improvement from him from camp to camp."