ESPN Bills reporter Mike Rodak details why Vontae Davis was in the lineup and the struggles the team had seen from him in the preseason. (1:08)

ORCHARD PARK, N.Y. -- Buffalo Bills cornerback Vontae Davis abruptly retired at halftime of Sunday's 31-20 loss to the Los Angeles Chargers, saying in a statement later that the reality had hit him: "I shouldn't be out there anymore."

Davis, a 10-year veteran, said he meant no disrespect to his teammates and coaches, but that physically he could no longer play at the standard he set for himself.

"[He] pulled himself out of the game," Bills coach Sean McDermott said. "He communicated to us that he was done."

Linebacker Lorenzo Alexander alerted reporters to Davis' abrupt retirement after the game.

"Never have seen it ever," Alexander said. "Pop Warner, high school, college, pros. Never heard of it. Never seen it. And it's just completely disrespectful to his teammates. ... He didn't say nothing to nobody. ... I found out going into the second half of the game. They said he's not coming out, he retired. That's it."

After the game, Davis released a statement on social media.

He talked about the physical toll of the game and said that while he was on the field Sunday, he didn't feel right and wondered whether he wanted to keep going.

"And truthfully, I do not because the season is long, and it's more important for me and my family to walk away healthy than to willfully embrace the warrior mentality and limp away too late," he said in the statement.

"This was an overwhelming decision, but I'm at peace with myself and my family."

Davis started Sunday's game but was not seen on the field or on the sideline in the second half. The Bills trailed 28-6 at halftime.

"I don't have nothing to say about Vontae," Alexander said after the game. "I'm going to give him a little bit more respect than he showed us today, as far as quitting on us in the middle of the game."

Davis, 30, was a healthy scratch for the Bills' regular-season opener in favor of Phillip Gaines, who started the Bills' 47-3 loss to the Baltimore Ravens. Gaines played nickel cornerback for the Bills on Sunday after an injury to rookie Taron Johnson in the season opener.

Gaines dislocated his elbow in Sunday's game, a source told ESPN, but there is hope that with treatment he will be able to play next Sunday in Minnesota.

The Bills signed Davis to a one-year deal in February that included a $2.25 million base salary and a $1.5 million signing bonus. Of his base salary, $2 million is fully guaranteed. He also was due roster bonuses of $15,625 per game on the 53-man roster and $46,876 per game on the 46-man game-day roster.

McDermott, talking about how he will address Davis' departure moving forward, said, "When I get back in here, we'll continue to communicate on what exactly is going on there, and we'll go from there."

In other defensive developments, McDermott took over playcalling duties from defensive coordinator Leslie Frazier in the second half of Sunday's game.

"I just felt like we needed a spark," McDermott said. "That's my background. Coach Frazier does a really good job, as well as the defensive staff. I just felt like we needed a spark."

McDermott said he would evaluate the playcalling situation and "a lot of other things" after the loss.