Researchers have shown that playing in a single professional football game is the equivalent of putting your body through a moderate car accident. That's why NFL teams only play once a week.

Rules have changed to protect players, safety being paramount after studies surrounding concussions and CTE were published. The movie Concussion, starring Will Smith brought the issue even more to the forefront.

Throughout the history of the NFL, some players have shown us the true meaning of gladiator, as they step out on the gridiron with absolutely no business being there, injured to the point where they should be home resting rather than putting their bodies on the line, play after play.

1. Ronnie Lott - San Francisco 49ers

Ronnie Lott was one of the greatest safeties to ever play the game, but it's not his ability on the field that has him enshrined in football lore, it is his raw toughness and commitment to the game he once played.

Lott broke his pinkie finger so bad in 1986 that it looked to require reconstructive surgery. Instead of having the surgery done, and then dealing with a long recovery process, he opted to amputate the finger at the top knuckle so that he could get back out on the field as quickly as possible.

Would you give up your finger to get back out on the field?

2. Jack Youngblood - Los Angeles Rams

With a name like Jack Youngblood, you expect the man to be a monster on the field, and a monster he was. He was one of the most feared defenders to ever take the field. But it is not his accolades that hold the highest regard of his past opponents, it was his gutsy performance during the 1979 playoffs.

He played the entire playoffs including the Super Bowl, with a broken fibula in his left leg. Think about that for a moment. A game that requires you to run at high speeds while purposefully attempting to crash into other gigantic sized men, was played at the highest level on the biggest stage, by a man with a broken leg.

3. Matt Stafford - Detroit Lions

Matt Stafford was drafted first overall in 2009 by the beleaguered Detroit Lions, a team that had gone 0-16 the year before. High hopes and huge expectations were placed on the young quarterback's shoulders, and he wasn't about to disappoint. During a game late in November of his rookie season, the Lions were up against the Cleveland Browns, losing late in the fourth quarter. Stafford drove them down the field before being hammered into the turf by a Browns defender, separating his left shoulder.

He was pulled off to the sideline with one play left in the game. With his left arm hanging uselessly by his side, he forced his way back into the game to throw the game winning touchdown, earning him the respect of his teammates and Lions fans alike.