(AP) — Travis Frederick said he thought he played well at center for the Dallas Cowboys after returning from a nerve disorder that sidelined him for an entire season.

The 2016 All-Pro made it clear Monday it wasn’t good enough.

Frederick retired from the NFL at 29, saying he “could no longer perform at my highest level” even though he went to his fifth Pro Bowl in his only season after recovering from Guillian-Barre syndrome.

“Each day, I faced a struggle: I could no longer perform at my highest level,” Frederick wrote in a long statement posted on Twitter and released by the team. “Playing ‘well’ is not what I expect of myself and not what my teammates deserve. Because of this, I know my days as a football player are done.”

A first-round pick seven years ago, Frederick missed all of 2018 after getting diagnosed with the auto-immune disease during training camp.

According to the National Institute for Neurological Disorders and Stroke, Guillain-Barre causes the body to attack a network of nerves around the brain and spinal cord. Most people recover from even the most severe cases, which can include temporary paralysis, but some will continue to have some degree of weakness, according to the institute.

Frederick was asked frequently how he was feeling and how he thought he was playing during a season that started with high expectations for the Cowboys but ended without a trip to the playoffs. The former Wisconsin player’s answers were always upbeat, including during his final session with reporters after the season ended.

The final answer was something different, and leaves a big void in the middle of the offensive line. The Cowboys have invested heavily there with draft picks and subsequent contracts for a decade.