Bills spokesman Scott Berchtold said he was informed by the team's medical staff the player went into surgery at a Buffalo hospital at about 8 p.m. ET. Berchtold said he had no further information and didn't know whether Everett had shown any signs of movement since he being driven off the field in an ambulance.
Coach Dick Jauron said immediately following the game that the player sustained a cervical spine injury, but wouldn't discuss the severity of the injury.
The player's agent Brian Overstreet was not immediately available for comment.
The game was delayed for about 15 minutes, and the Bills gathered at the sideline while doctors attended to the player.
Everett's injury cast a pall over the Bills following a season-opening 15-14 loss, with several players expressing concern about their teammate.
"It was real hard," cornerback Terrence McGee said. "I watched the whole thing, and he never moved. ... It's real sad to see him go off on a stretcher, but we hope he's OK."
"It's real sad," added receiver Roscoe Parrish, who played with Everett at the University of Miami. "When something like that happens to a close friend of yours, and you know how much he loves football, it bothers you."
Denver players expressed concern, including kicker Jason Elam, who kicked the winning field goal as time ran out.
Before taking questions after the game, Elam said: "What we heard is not good, so for our whole team, our prayers go out to him."
Buffalo's third-round draft pick in 2005, Everett missed his entire rookie season with a knee injury and spent most of his second season limited to special-teams duty.
The Bills liked Everett's 6-foot-4 frame and were counting on him to play a role in their passing attack this season.
Everett's injury was the most severe but far from the only one sustained by Bills players during the game. Buffalo also lost three defensive starters to injury.
Starting free safety Ko Simpson is out indefinitely after breaking his left ankle. Starting cornerback Jason Webster is out indefinitely after breaking his forearm in the fourth quarter. And then there's linebacker Coy Wire, filling in for injured starter Keith Ellison, who sprained his knee in the first quarter.
Simpson was hurt when he had his feet cut out from beneath him by teammate Jason Webster as the two were attempting to tackle Broncos receiver Javon Walker. Simpson fell immediately to the ground and was unable to put any weight on his left foot.
Team trainers were forced to lift the player onto a cart and he was taken for X-rays.
Buffalo's fourth-round pick in the 2006 draft, Simpson started 15 games last season and was a member of the NFL's youngest safety tandem, playing alongside rookie first-round pick Donte Whitner.
Wire was examined on the sideline but made his way to the locker room on his own. Reserve Mario Haggan replaced Wire.
It's unclear when Webster was hurt. The Bills had signed the seven-year NFL veteran last spring to take over as starter after losing Nate Clements to San Francisco in free agency.
The injuries were the latest blows to an already banged-up and young defense that was starting four players with less than two years of NFL experience. Buffalo also lacks experienced reserves at defensive end, with Ryan Denney out indefinitely with a broken left foot and Anthony Hargrove suspended for the first four games for violating the league's substance abuse policy.
Copyright 2007 by The Associated Press.