"It shakes you around a bit," Hayne said with a laugh.
Well, that and a sore neck.
Hayne's attempt to convert from Australian rugby star to NFL player with the San Francisco 49ers got real on Tuesday, the first day the Niners put on the pads and hitting became the norm. And to be fair, Hayne more than held his own in the drill, in which the running back (Hayne) is essentially standing still while the linebacker (Moody) has a running start.
"I think every time a running back goes against a linebacker and you're able to put your body in front, that's what we're looking for," Hayne said the morning after, before referencing 49ers RB coach Tom Rathman.
"Tom's massive about that. Tom obviously had a great career here back in the day and he loves all that contact stuff. He'd do it every day if it was legal. It was good to get it out of the way."
Two Australian television crews were on hand for Haynes' first day of hitting, and while it has long been thought that his best shot at making the team would come on special teams as a returner, he was also getting run with the first-team offense on Wednesday night, behind second-year back Carlos Hyde.
"As a running back, you've just got to really know where you're running and who you're running off and kind of anticipate what the defense is going to do ... find the gaps and the holes, the spots in the defense."
Niners special teams coordinator Thomas McGaughey Jr. was asked what skills he saw in the rugby-playing Hayne that could translate into an NFL-caliber returner.
"Just natural open field run skills," McGaughey said. "All you've got to do is just go to his YouTube highlight tape and you see it. He can stick his foot in the ground, he can make people miss. He's an excellent fielder of the ball, works extremely hard, very conscientious and he's a tough kid."
"I think he has the ability to do it. He just has to go do it."
Hayne obviously took hits in Australia, but there is more gear to wear and carry about in football.
"I think the biggest thing is you wear a helmet and shoulder pads," Hayne said. "You go a lot harder into tackles and you go with a lot more force. It does impact you differently. For me, I've just got to keep working on my game and figure out the best fix that's going to put me in the best position to either pass-protect or even run the ball."