The 30-year-old Davis, in his 10th NFL season, did not return for the second half of the Bills 31-20 Week 2 loss to the Los Angeles Chargers.

“Today on the field, really hit me fast and hard: I shouldn’t be out there anymore,” Davis said in an Instagram posting, adding he meant no disrespect to his teammates or coaches.

“While I was on the field, I just didn’t feel right.”

Teammates were shocked and stunned.

“I never have seen that. Pop Warner, high school, pros …. It’s just completely disrespectful to his teammates,” said Buffalo’s Lorenzo Alexander. “They said he’s not coming out. He retired.”

Bills coach Sean McDermott declined to go into details about Davis.

“He pulled himself out of the game. He told us he was done,” McDermott said.

Buffalo signed Davis to a one-year, US$2.5 million (RM10.3 million) deal in February that included a US$1.5 million (RM6.2 million) signing bonus.