Dallas Cowboys center Travis Frederick announced his retirement via Twitter on Monday night.
While the move came as a surprise to the Cowboys, sources said there had been rumors that Frederick, who just turned 29, might walk away.
Frederick has battled Guillain-Barre syndrome, an autoimmune disease that affects the nervous system, which kept him off the field in 2018.
"I made my return to the field, played well overall, and was selected to the Pro Bowl, but it was a difficult year for me," Frederick said in his announcement.
"Each day I faced a struggle: I could no longer perform at my highest level. Playing 'well' is not what I expect of myself and is not what my teammates deserve. Because of this, I know my days as a football player are done. I am proud of what I have accomplished in my career, and I walk away with my head held high."
The Cowboys signed Frederick to a six-year, $56.4 million extension before the 2016 season that included $28 million in guaranteed money.