Today's NFL players know more about the effects of violent hits than their predecessors did. They know that hits to the head can destroy or damage the brain. They know that former NFL players struggle with everything from dementia to sore backs.

Today's NFL players belong to a brotherhood of elite athletes, and a union that pleads for the league to care more about their well-being.

No matter. Today's NFL players spend Sundays trying to fold their brethren like origami.

They level each other with vicious blind-side hits. They aim at each other's heads, and use their own helmets as weapons. They show even less regard for their opponents than they do for themselves.

They risk their health for their teammates and families, to pay their bills and sate their bloodlust. This week, I asked three generations of hard-hitting NFL defensive backs whether they ever felt empathy for their opponents, either in the split-second before collision or in the moments after leaving a player writhing on the turf.

In a word, each said, "No.''

Vikings coach Leslie Frazier starred for the famous 1985 Bears defense before a knee injury ended his career. Vikings cornerback Antoine Winfield, who weighs about 185 pounds, is one of the best tacklers in recent league history. Harrison Smith, the team's first-round draft pick out of Notre Dame, is starting at safety as a rookie.

All three come across as smart, classy and unapologetically ruthless.

"I think you have to try to hit a guy as hard as you can every chance you get,'' Frazier said. "You've just got to do it within the rules. I don't think you'll ever see a coach or a player say, 'Oh, you hit him too hard, what are you doing?' You just don't want a foul, so you don't want to hit a guy in the head.

"You don't want to see a guy get injured. But you're never thinking, 'I don't want to hit him too hard.'"

Frazier has watched the league and society take a different view of violent hits. He has not witnessed a changed mentality in locker rooms.

"There really weren't any rules like that when I played,'' he said. "You recall back then, all about big hits, that were sold. They were a big attraction. I remember having camps with kids and showing videotapes of some of those hits. Now those tapes aren't produced anymore. They're disdained. They're shunned. It's a different time.''

He sounded nostalgic.

Winfield spent Tuesday burying his younger brother in Akron, Ohio. Wednesday, he said that reminder of life's fragility won't keep him from leveling opponents. Quite the opposite.

"No one's guaranteed tomorrow, as I learned very quickly,'' he said. "I live day to day, live life to the fullest, and if I'm messed up down the line, so be it.

"I've been taught to play this game one way, full speed, go as hard as you can. I can't ease up. I'm 185 pounds going against 230-pound running backs and 6-4, 200-pound wide receivers, so I can't go in half-stepping. I have to put all 185 on them.''

Smith attended Notre Dame and grew up watching a different game than did Frazier and Winfield. He has seen flags thrown for taps to a quarterback's head. He has been taught that hitting a defenseless receiver is a penalty. He has adapted because of the rules, not stray thoughts about mercy.

"I agree with Coach Frazier; it's not that you're going out with the intent of injuring someone, but it's a violent game,'' Smith said. "It seems like they're trying to tweak that, but at the end of the day, it's a violent game, and if you're out there, you have to play that violent game.

"If someone gets hurt or if you get hurt, well, you signed up knowing that could happen.''

Ask an NFL defensive player about sympathy, or empathy, and you get funny looks.

"I'm a different guy,'' Smith said. "I don't think about it. I don't think about the future much. I'm out there playing as hard as I can. I don't worry about that stuff.

"Like I said, it's what we all signed up for.''

Jim Souhan can be heard Sundays from 10 a.m. to noon and weekdays at 2 p.m. on 1500-AM. His Twitter name is SouhanStrib. jsouhan@startribune.com