DENVER - In a sports stadium crammed with 67,000 fans, the most chilling sound is no sound at all.
When Broncos defensive lineman Derek Wolfe dropped to the turf in Seattle, it was close to silent inside CenturyLink Field. Too close to be comfortable.
Too close not to wonder: Is football worth it?
On a normal rushing play, Wolfe, a 285-pound mountain of a man, was hit low, then hit high. The second hit smashed into his helmet, or his neck, or both.
It's hard to tell, and after the fifth or sixth replay I elected not to watch again. I was never good with horror films.
On came the stretcher. On came the ambulance.
Roughly 20 or 30 minutes later, on came the next play, just as vicious as the last.
"If you're asking me if I've ever been carted off in an ambulance (before), no," Wolfe said. "I don't like that feeling at all. So let's try not to let it happen again."
It will happen again, whether that's in Saturday's preseason game between the Broncos and Rams at Sports Authority Field, on a Friday in a high school game, on a Saturday in a college game or in another NFL game this season.
This is a game we love. Here was a sudden reminder it's also one we should fear.
"If you play scared, you're going to get hurt again," Wolfe said.
It's easy to appreciate D-Wolfe, the football player, for his blue-collar approach to his chosen profession. He's an Ohio boy who competes with an edge, and the Broncos coaches dig that about him.
There's just enough old-school to his game that he holds a grudge against the teams that, in his mind, let him fall to the second round of the 2012 draft.
He's also really, really lucky and said so himself.
"I get a little emotional about it, because this is what I love to do and I couldn't imagine myself doing anything else," he said.
Wolfe said he suffered a cervical strain. He lost feeling in his limbs. Just 23, Wolfe admitted the result could have been much worse. It certainly looked much worse, enough so that a packed stadium delivered the cold sound of quiet.
"You see the ambulance come out there to pick him up..." linebacker Wesley Woodyard said, his voice fading off.
In a Broncos offseason with more tricks than treats, the scariest moment arrived Saturday night, a jarring reminder of how merciless this game is.
The best moment came a few days later, when Wolfe met with assembled media and declared his neck is sore, but will be fine. He hopes to play in the season opener against the Ravens on Sept. 5.
Frankly, I'm surprised more players aren't injured on the football field, severely or otherwise. Up close, the speed, size and the viciousness of the NFL game is startling.
It's a win simply if the ambulance stays parked.
There's a documentary scheduled for release in October. It's a PBS production entitled "League of Denial: The NFL's Concussion Crisis." The New York Times reported the NFL pressured ESPN to withdraw from the investigative project.
I suspect the two-part series will open more eyes, smack in the middle of the NFL season.
The question is sure to come up: Is football worth it?
When Wolfe lay motionless, shielded from view by medical personnel, I thought it was Mitch Unrein, the defensive tackle from Eaton. It could have been. Or it could have been Kevin Vickerson or Sylvester Williams or Robert Ayers or Von Miller or Danny Trevathan or Woodyard or any one of the Broncos or Seahawks. Football's dangers don't discriminate.
"D-Wolfe is like a brother to me," Woodyard said.
The hit that dropped Wolfe was a nasty one. It was also a legal one, with no fines assessed by the NFL.
And so the games will go on, and somebody will get hurt.
You just hope he gets up.