MANKATO - Saturday morning, the veterans on the Vikings defense welcomed rookie running back Toby Gerhart to the NFL by treating him like a hacky sack at a beach party. They smacked him to the ground, then taunted him, offering an early reminder that violence is a defensive player's milieu, his currency.

Even these hardened men turned away on the night of Dec. 6, 2009, when E.J. Henderson, their star middle linebacker, sprawled on the field in Glendale, Ariz. As Henderson chased a Cardinals running back, Vikings safety Jamarca Sanford submarined Henderson's left leg, breaking his femur.

Most Vikings recoiled. Some cried. After the game, many were still oscillating like survivors of a car crash.

Less than nine months later, Henderson is on the Vikings' active roster and taking part in training camp, offering proof that NFL players are wired differently than most humans and insight into why the NFL has become the most popular game in America.

"I had never even heard of something like that happening, you know what I mean?" said former Vikings linebacker and assistant coach Pete Bercich, who coached Henderson and now is an analyst on Vikings broadcasts. "A guy breaks his femur like that, I don't know if coming back like this is crazy, or unique, because I had never heard of it or seen it.

"It is a remarkable thing, to snap the biggest bone in your body and just go back out there. I think it's amazing he'd even want to go back out there after something like that. In the NFL, you can truly say that these guys are putting their life and limb on the line. You can't say that about basketball, or baseball. But, unfortunately, we've had some people die on the field."

The NFL has eclipsed games of skill by becoming a game of remarkable speed and violence, by making football games into thrillers in which the actors do their own stunts. "I don't recommend this job," said defensive end Jared Allen. "I think someone once said it's the equivalent of getting into a 25-mile-an-hour car crash, and for linemen, it's every single day -- and especially on game day.

"We get maybe a day off, a day and a half, and we're back on the field working. Our bodies go through a lot. I think that's also why we can recover fast. Where most people might take years because they feel a little pain, we're used to a little pain.

"E.J.'s a tough enough kid that he'll get through it. You sacrifice like that for the greater good of the team. I think that's why we have the best sport."

If football is not the "best" sport, it is undeniably the sport of the times, a game perfectly married to high-definition, big-screen televisions, instant replay and incessant analysis. What makes the game compelling -- "Sopranos"-level violence -- leaves players battered and worn as driftwood.

Henderson's injury and recovery are unique in football only because of the details -- a broken femur repaired by a titanium rod is unusual, even in this game.

"Why do we get paid so much? Because we put our lives on the line every single day," tight end Visanthe Shiancoe said. "We can die. A couple of years ago, somebody died on this field, right?

"You're talking about head trauma, you're losing brain cells every day. We're crazy."

Shiancoe nodded to the fields at Minnesota State Mankato, where Vikings tackle Korey Stringer collapsed after suffering heat stroke during training camp in 2001.

Henderson, standing a few feet away, spoke of his injury as if he had done nothing more than sprain an ankle.

"I think football is so fast, you don't really have the time to be scared, or think about a hit to the leg," he said. "You have to put that out of your mind."

Or retire.

"From the first day, he told me, 'I'm going to change the protocol with the way this injury is rehabilitated,' " coach Brad Childress said. "I thought, 'Wow, there is a mouthful.' He had his jaw locked from the beginning. He has been religious about his rehab, almost to the point where you have to hold him back."

It's good work, if you can survive it.

Jim Souhan can be heard at 10-noon Sunday on AM-1500. His Twitter name is SouhanStrib. • jsouhan@startribune.com