Fans know that pro athletes play through tremendous pain in physical sports like football. And we know that players will often deny symptoms — even symptoms of concussions — to stay on the field.

Last season, San Diego Chargers guard Kris Dielman waved off officials and stayed in the game after suffering a fourth-quarter concussion. Then he had a seizure on the flight home.

New York Jets quarterback Greg McElroy serves as the latest example of the disturbing trend.

The third-string quarterback, who was promoted to starter after the struggles of Mark Sanchez and Tim Tebow, missed the Jets’ final game with a concussion. According to Jane McManus of ESPNNewYork.com, McElroy confided in teammates but initially chose not to reveal his head injury to the Jets’ coaches or medical staff.

Tebow, who had been passed over for the starting role in favor of McElroy, said that players could tell something was wrong with the rookie quarterback. “He didn’t look exactly right at the beginning of the day.”

Fighting headaches while weightlifting, McElroy finally discussed his symptoms with the Jets’ athletic trainers. Head coach Rex Ryan immediately decided to remove McElroy as starting quarterback.

One of the players with whom McElroy had admitted his head injury was wide receiver Clyde Gates, who suffered a concussion himself earlier this season. He told ESPNNewYork.com that he listened to McElroy’s concerns and shared his own experience.

“He was hurting real bad. I was like, ‘Bro, I know, I’ve been down that road already. I’m just saying you can’t try to tough it out cause you going to end up hurting yourself. You’ve got to let everybody know how you really feel.’ ”

The fear of losing his starting job might have made McElroy reluctant to disclose his injury.

Earlier this year, 49ers quarterback Alex Smith personally reported his concussion and ultimately lost his starting job to backup Colin Kaepernick. Likewise, Michael Vick lost his job to backup Nick Foles after a concussion. Maybe these were performance-based decisions unrelated to the head injuries, but it is easy to understand the players’ perspectives.

Tebow has dealt with concussions as well and acknowledges the dilemma for McElroy and other players. “You fight hard to earn something and you don’t want to jeopardize that with an injury for sure. I think that’s definitely something guys will think about.”

Ryan stressed that McElroy needed to be honest with the team’s athletic trainers. “I think, hopefully, this will be an example to all the players. Because the worst thing that could’ve happened is he would’ve gone out there with nobody knowing how he really felt and hurt himself.”

Ryan is absolutely right. We know that if a players’ brain hasn’t completely recovered, he risks a second impact that could cause much more serious brain damage.

Plus, concussions can be a slippery slope. The first concussion usually requires a major blow to the head. But the amount of force required for subsequent injuries drops if the brain hasn’t returned to normal. Players then often start suffering concussions after what seem like minimal hits.

I understand McElroy’s and other players’ concerns of losing their spots on their teams. But they need to fear long-term brain damage even more.

Dr. David Geier is an orthopaedic surgeon and Director of MUSC Sports Medicine. For more information about football injuries and other sports medicine topics, go to Dr. Geier’s blog at drdavidgeier.com.