A recently retired Chicago Bears player sent regrets about the schedule conflict that interfered with him seeing a private screening of “Concussion.”

“Wish I could, thanks for the offer,” he texted. “I’m a little scared to watch that movie.”

He should be.

But that former player needs to see it anyway. So does every former or current NFL player and coach, every fan who cheers the big hits every Sunday, every media member who covers the weekly carnage, everybody tangentially connected to America’s most popular game. The masterfully done movie by Columbia Pictures, to be released on Christmas Day, is a horror film disguised as a drama, 2 hours and 2 minutes as haunting to a football audience as it is powerful.

Liking fooball never has been more complicated, but loving it no longer can be unconditional, something seeing “Concussion” underscores.

The NFL cannot ignore this movie and the portrayal of its resistance to the findings of chronic traumatic encephalopathy (CTE) by forensic pathologist Bennet Omalu, the film’s hero played by Will Smith. The league cannot dismiss with silence or smugness the way the story depicts the NFL as unsympathetic to brain injury as Big Tobacco was to lung cancer.

A football person I respect offered a good reminder that it was a Hollywood dramatization full of poetic license and creative liberty.

But there was nothing fabricated about the way Pittsburgh Steelers Hall of Famer Mike Webster spent his final days living in a truck before he died at 50, the tragedy that led to Omalu’s discovery of CTE in Webster’s brain. There was nothing fictional about former Steelers lineman Justin Strzelczyk driving his truck into oncoming traffic at 90 mph to kill himself at 36 because he believed he was losing his mind. There was nothing fake about the helplessness former Philadelphia Eagles safety Andre Waters felt after ending his NFL career and before shooting himself at 44. Or the despair former Bears safety Dave Duerson revealed in the suicide note he left before he shot himself in the chest to preserve his diseased brain for study. These sad, steady declines are documented.

One of the most gripping exchanges in the movie involves a desperate Waters asking Duerson for help in 2006 outside the league office in New York. Duerson, then a trustee on the NFLPA Retirement Board, essentially told Waters to toughen up, showing a lack of understanding and empathy for his suffering. Five years later, both men would be dead from self-inflicted gunshot wounds Omalu believes were related to brain trauma their careers as NFL safeties caused.

Some scenes were hard to watch; a disoriented Webster mutilating himself, a deranged Strzelczyk grabbing his wife, a different Duerson than Chicago remembers getting into bed with a gun before his final act. As difficult as the images are to digest, NFL players such as Bears offensive tackle Jermon Bushrod grasp the importance of seeing them — and trying to understand them as they relate to the delicate balance between a player’s responsibility and the league’s obligation.

“I get why guys don’t want to see it, to see that reality, but when you’re a part of it, I’d think you’d want to do whatever you can to help yourself out,” said Bushrod, whose concussion in Week 3 has affected his season. “Guys in our position have to realize it’s a risk every day you step onto the field.”

Bushrod credited the NFL for making the game safer than it was when he entered the league in 2007, the contention of Julian Bailes, a neurosurgeon who is co-director of the NorthShore Neurological Institute. Bailes, portrayed by Alec Baldwin in the movie, claimed in a national conference call with reporters that “we don’t have an epidemic on our hands” regarding CTE despite widespread fears and called the risk to current players in light of reforms “very small.”

“The NFL has made sweeping changes,” said Bailes, the former Steelers team physician who befriended Omalu during the Webster autopsy. “We’ve done almost all we can do to reduce unnecessary or gratuitous head contact whether it’s practice or games. The sport may continue to evolve some more in the future. We may need to take linemen out of the three-point stance (or) eliminate punt returns or other high-velocity plays.”

“With the changes that have occurred to reduce or eliminate head contact in practice and eliminate open-field direct head hits, I think that football is safe as long as the players and their parents understand the risk and the pros and cons and the benefits and potential risk of participating,” Bailes said. “It’s a personal decision.”

So is seeing the most important movie about football ever made. But everybody associated with the sport who decides to view it with an open mind will be grateful they did.