The movie Concussion premiered in theaters on Christmas Day, and tells the story of a medical specialist who discovers a degenerative brain disease that is linked to contact sports such as football.

In the Concussion movie, Will Smith plays a pathologist named Dr. Bennet Omalu who discovers a disease known as Chronic Traumatic Encephalopathy or CTE, which affects athletes who have engaged in contact sports.

As the issue builds on how football leagues such as the NFL would take care of its athletes and prevent them from suffering from this disease, some former players have also weighed in on the discussion.

#ConcussionMovie “opens the light and shows us what we’re experiencing.” – Former pro football player Calvin Snowden https://t.co/vArJbZNjyg

— Concussion Movie (@ConcussionMovie) December 28, 2015

Former Oiler Warren Moon said in an interview that he suffered six concussions during his career, and he is now worried about their long-term effects on his health.

“Your brain gets rattled around in your skull, so it bruises your brain,” Moon said.

Moon, 59, remembered the different concussions he suffered, and recalled that some of them were very bad that he would occasionally lose awareness of where he was.

He was worried that due to the concussions, something bad would happen one day.

Hall of Famer Warren Moon Discusses the Consequences of Football-Related Concussions

While Moon still hasn’t experienced the adverse effects of the sport, other former players are not as fortunate. Some have reportedly suffered from Alzheimer’s disease, ALS, while others eventually died from their injuries.

One of the former NFL players who is currently suffering the consequences of his numerous concussions is Hall of Famer Harry Carson.

“I would not have played.” Harry Carson, Darrelle Revis open up on the NFL’s terrifying concussion reality https://t.co/1D8Hi1QLtl

— New York Post Sports (@nypostsports) December 20, 2015

Carson, who played as linebacker for the New York Giants in the 1970s and ‘80s, said that parents should be well-informed regarding what their kids will go through if they play football.

The Concussion Movie Delves into Brain-Related Injuries in the NFL

The Concussion movie which also stars Alec Baldwin and Albert Brooks, was supposed to spread awareness on this danger. However, a report pointed out that the film seemed to have softened some of the crucial plots, and script somehow focused its tone on other related issues, reportedly to avoid earning the ire of NFL executives.