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For many years, NFL rules have allowed ball carriers, usually quarterbacks, to protect themselves by sliding feet-first. But this year that rule is changing — a significant change that has received little attention.

In 2018, the NFL is considering a player to have given himself up if he dives head first, the same way a player has given himself up when he slides feet first. That means a player can’t be hit after he goes into a head-first dive, and it also means the ball will be spotted at the point where the player began to dive, rather than at the point where the player finished moving forward.

“A quarterback does not have to slide feet first to be considered to be giving himself up,” the league’s online rules say. “Regardless whether the slide is feet first or head first, as long as he gives himself up, he should receive the protections afforded to him as a player in a defenseless posture.”

It’s easy to see how big a change that will be: In the past, if a quarterback ran the ball on third-and-5, he’d usually slide feet first once he picked up the five yards, but he’d dive head-first and try to pick up the last yard if he was met by an opposing defender after gaining four yards. Now, there’s no distinction between feet first and head first.

Officials say that’s a major change.

“It’s a big change this year,” line judge Rusty Baynes told ESPN. “Because if you were a runner or a quarterback and you dove head first you could, if you were untouched, get all of that slide. If you went head first. Now, you cannot. It’ll be interesting to see what happens at the goal line.”

Interesting indeed: Imagine it’s fourth-and-goal in the final seconds of the game, a quarterback whose team trails by five points drops back to pass, then sees an opening in the middle of the field, runs toward the end zone, and just as a linebacker approaches at the 1-yard line the quarterback dives head-first into the end zone. That won’t be a game-winning touchdown anymore. It will be the quarterback giving himself up at the 1-yard line. The first time that happens, there’s going to be outrage from players, coaches and fans of the losing team.

This change hasn’t received much attention because it’s technically a “point of emphasis” and not a “rule change.” But whatever you call it, it’s a major difference in the way the game of football is played. And a whole lot of people won’t be happy about it.