The truth on consequences created by the NFL's new Crown-of-Helmet rule will not be fully realized for some time, perhaps several seasons.
However, even before the change is played out on the field, enlightened conjecture on potential ramifications yields troubling and fascinating possibilities. They include a different series of troubling injuries and a more exciting exhibition of talent in the open field, the NFL's version of "Dancing with The Stars."
The rule prohibits ballcarriers and tacklers from initiating contact with the crown of their helmet when they are outside the tackle box. This should not affect those brutal, head-on collisions between the tackles on short-yardage and goal-line plays. But beyond that, literally, there could be dramatic changes.
Pitched as a safety measure to limit concussions, it could result in a trade off of those neurological concerns for a myriad of other injuries, including legs, hips, knees, ribs and a possible increase in paralysis from compacted spines, which would be ironic considering the original purpose of the rule.
From a game play standpoint, ball-carriers and tacklers may adopt new mannerisms that could result in more exciting open-field plays -- or boring increase in players opting to run out of bounds.
As expected, initial reaction from retired and active running backs is mostly negative. The idea of being penalized -- 15 yards and possibly a few thousand dollars -- for executing a move that is almost intuitive or second nature to many runners is not easy to embrace.
Hall of Fame running backs Emmitt Smith and Marshall Faulk are adamantly against it, calling it "ridiculous" and claiming it will change how the game is played.
Ridiculous or not, the intent of the rule is indeed to change how the game is played, which could be a dramatic difference for some and almost no difference for others.
It all comes down to a matter of style.
Some of the best running backs in NFL history did not rely on their helmet to barge for extra yardage. They used some combination of agility, guile, quickness, shoulders, straight arms, toughness and will to keep going.
Helmets do not come to mind when recalling the great runs of Jim Brown, Gale Sayers, Barry Sanders, O.J. Simpson, Eric Dickerson, Tony Dorsett, Marcus Allen, Curtis Martin, Eddie George, Adrian Peterson and Franco Harris.
Brown ran through, bounced off or straight-armed defenders and Peterson's style is similar.
"I didn't use my head," said Brown, now 77 and fit for a fight in appearance. "I used my forearm, the palm of my hand and my shoulder - and my shoulder pads. I wasn't putting my head into too much of anything. I don't think that's a good idea."
Sayers combined vision with graceful and stunning lateral agility, as did Allen. Simpson was similar, but with world class speed. Dorsett, Dickerson, Martin, George all avoided contact while seeking a crease, then took one cut and were gone. Harris gathered as many yards as his blocking allowed, then ran out of bounds. And Sanders, well, you just had to see it to believe it.
This in not to say helmets were not a primary weapon of some of the greatest runners in NFL history.
Emmitt Smith, the career record-holder with 18,355 yards, admits his helmet was part of his arsenal.
"I used anything and everything I could to keep going," Smith said. "If that meant putting my helmet into a defender, that's what I did."
The late, great Walter Payton also used anything and everything to gain the second most yards in NFL history, 16,726.
Most of the NFL's greatest power runners often lowered the crown of their helmet to blast through defenders. They include Earl Campbell, John Riggins, Larry Csonka, Jim Taylor, Jerome Bettis, Marion Motely, Bronco Nagurski, Christian Okoye and Mike Alstott.
How would they have done if they played under the constraints of this new rule? Hard to say.
Campbell, at least, had extraordinary speed and thighs the size of redwood trees. He would be a nightmare to tackle in any era, under any rules and probably even with no helmet at all. Not coincidentally, the great former Houston Oiler -- the man legend known as the Tyler Rose -- is now able to get around only with the help of a cane or a walker.
With all that in mind, including the consequences paid by Campbell, it will be interesting to see if and how players react to the new crown-of-helmet rule. That includes ballcarriers and tacklers.
Imagine a ballcarrier 15 yards downfield on a collision course with a safety in the middle of the field. Mindful of the new rule, the back might remain erect while approaching the defender. Likewise, the safety would keep his head and body up. Instead of a helmet-to-helmet collision, there might be a matchup with more finesse, balance, lateral agility and guile. And there it is, the NFL's version of "Dancing with the Stars."
Of course they might still simply collide legally, leading with their shoulders and keeping their heads and helmets up and more or less out of the way. We might see more of those old textbook tackles that involve shoulders, arms, wrapping up, pulling in, slamming to the ground.
Yet with the helmet out of the way as an instrument of destruction and concussions, there could be a proliferation of other injuries. Keeping one's head up shortens the spine, creating the possibility of increased compaction injuries that lead to temporary or permanent paralysis. Some reports indicate that former New England Patriots receiver Darryl Stingley had his head up and was braced for impact when he was paralyzed by his mid-are collision with Oakland Raiders safety Jack Tatum in the 1970s.