The new helmet rule has become a real headache.

Monday afternoon, when they might have been otherwise engaged, the Eagles' defensive players watched tape compiled by the team's video department of the legal and illegal hits through the first two weeks of preseason games, as enforced under the NFL's newest and most controversial safety measure.

After practice, the defensive backs were scheduled to spend an extra 15 to 30 minutes practicing what they hope will be considered legal hits in Thursday night's game at Cleveland. They do this once a week.

They need all the help they can get. So does the league.

The Eagles have drawn five penalties in relation to the helmet rule. Two of the three at New England came after the ballcarrier lowered his head first.

Yes, the record 281 concussions reported in 2017 might warrant stricter rules, especially in the wake of the spinal injury to Steelers linebacker Ryan Shazier.

Yes, new rules are often overemphasized in the preseason. Yes, the refs might retract their claws when real games start.

In the meantime, players and coaches trying to prepare for the season are bewildered and outraged, justifiably so.

"Honestly, I don't know how we're going to adjust to it," said safety Corey Graham, who, as a 12-year veteran, watched Brian Dawkins ride hellacious hits to Pro Bowls, then played with Ed Reed in Baltimore. "I don't know what we're going to do. We don't know how it's possible."

No one endorses kill shots anymore. No one wants to see "snot bubbles," as former Eagles cornerback Troy Vincent, a terrific hitter, described the result of his generation's knockout blows — ironically, of course, because Vincent now oversees rule enforcement as the NFL's vice president of football operations. But when a defensive back can't tackle a full-steam running back with his shoulder, we've passed over into the absurd. This was the case when Rodney McLeod drew a penalty Thursday at New England.

"For Rodney, when he hit the guy low, he was trying to hit the guy's legs," Graham said. "When you're trying to chop a guy's legs, you're hitting him with your shoulder. Your head's got to go down."

That sentiment infected Twitter the last three days, fueled by a viral tweet from agent Brett Tessler, who was advocating for his client, 49ers special-teams ace Raheem Mostert.

Mostert lightly clipped Texans returner Tyler Ervin's facemask as Mostert tackled him, although Mostert's intent clearly was to send his own head to the right of Ervin.

>> READ MORE: If the NFL actually wants to be safer, it's time to reevaluate tackling

By Monday the tweet had more than 2 million views. When contacted Monday, Tessler declined to comment on the tweet, but it had earned the endorsement of Mostert's teammate, Richard Sherman, and Jack Del Rio, who are two of the more significant defensive personalities in modern NFL history.

Del Rio, who played in the NFL for 12 years then coached for the next 21, complemented Mostert:

Sherman then doubled down:

The league's emphasis, as reiterated in the video below, is to penalize players on both sides of the ball for lowering their heads to initiate contact and creating a body posture that invites injury. The incidents in the videos are nicely edited and slowed down — luxuries officials and players do not have.

>> READ MORE: Legal or illegal? Malcolm Jenkins' Super Bowl hit exemplifies confusion over new rule | David Murphy

All of this is directed at limiting players' risk of concussions and chronic traumatic encephalopathy. Nobody wants to see another case of CTE to precipitate another suicide like Junior Seau's, or to see a hard-nosed runner like former Eagles fullback Kevin Turner overtaken by CTE, or to see families destroyed by a player like Aaron Hernandez, who killed himself in prison while serving a life sentence for murder, all the while suffering from one of the most extreme cases of CTE ever observed in a 27-year-old.

It should be noted that NFL officials are, by and large, incredibly good at what they do. To consistently make correct judgment calls on world-class athletes in real time at field level is something just short of genius. But to expect officials, players, and coaches to instantly adjust to new rules is just short of idiocy.

"We're trying to take our head out of it, we're trying to lower our target, and we're trying to keep our eyes from dropping to the ground," said Eagles defensive coordinator Jim Schwartz, who spent his year out of coaching in 2015 as a consultant to the NFL's officiating department. "Those are the things that we're trying to emphasize. But again, not all of those will equal not getting a foul, particularly if you get a moving target that works into your path. We're trying our very best and the players are trying their very best to comply with the rule."

Which means more film, more practice, and, for now, more penalties.

"I'm going to keep doing the form tackling I've been taught since I was 9 or 10 years old. If they call the [penalty] — come in the next day, watch film, see where they may have caught the flag and correct it," said cornerback Jalen Mills. "It's a learning experience for both players and refs. As time goes on, they're going to get better at the calls."

Maybe this will, indeed, work itself out. The league  is preparing an updated teaching video about the new helmet-contact rule, and discussion of the rule is expected to dominate a previously scheduled conference call involving league officials Wednesday, ESPN reported.

Maybe the league will reconsider and allow replay to determine if a helmet hit was legal; for now, only ejection hits are eligible for review. Maybe players will be healthier, and there will be fewer concussions in 2018 and less residual damage 20 or 30 years from now.

But in this moment, it feels as if the game is more in peril than the health of its players.

"At the end of the day," said Mills, "football is a survival sport."

With this sort of seismic change, you wonder if football can survive.

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