Adam_Lazar/iStock(CHICAGO) -- A teenage hockey player died suddenly after playing in a game from complications with mononucleosis – an infection he was not even aware that he had.

Gabe Remy’s teammates on the Chicago Fury said that they could see signs he wasn’t feeling well last week but just figured that it was symptoms of the flu or perhaps something similar.

"[He was] hunched over a lot. Feeling really tired, said his stomach was bugging him," teammate Joseph D'Alessandro told ABC News’ Chicago station WLS-TV. "You could tell he was in a lot of pain. He said there was pain in his shoulder blade, he was throwing up out in the locker room."

Remy insisted, however, that he would persevere through the pain and sickness even if he wasn’t feeling well.

"He was excited to play. We love our guys to be aggressive and to go out there and compete hard, and he never had a problem competing," said Al Dorich, head coach of the Chicago Fury.

According to D’Allesandro, Remy played well in his last game. "If it was your first time watching him you wouldn't have known the difference," he said.

Remy took a turn for the worse after the game and reportedly barely made it home. By early Sunday morning he was rushed to the hospital for emergency surgery to treat a ruptured spleen. He died later that day.

Doctors said his cause of death was complications of mono which neither Remy nor his teammates even knew he had.

Remy had only just graduated from high school this past June and had hopes of trying to pursue a professional hockey career but his sudden death has left his team devastated.

"I kind of, like, expected to come to the rink today and have him here, so. I'm kind of in shock still," said Zack Zeidel, teammate.

"I couldn't even walk toward my stuff," said D'Alessandro. “I kind of just sat there … I think it would have brought him some kind of comfort that he fought through that last game with all the guys that love him, and he loved.”

Dying from mono is extremely rare but complications can happen and lead to an enlarged spleen or massive enlargement of the tonsils and adenoids which can, but very seldomly, lead to death.

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