Merriman, who earned the nickname "Lights Out" when he was one of the NFL's most feared pass rushers, was placed on season-ending injured reserve Tuesday because of a right Achilles' tendon injury.
"After much consideration and unanimous professional recommendations stating that my Achilles is in danger of rupturing, I have been advised that it would be in my best interest to undergo surgery as soon as possible in order to prevent a major injury," Merriman said in a statement. "I would like to thank all of my fans for their continued support on my road to a full recovery and am looking forward to getting back out on the field."
Merriman is suffering from the same injury that forced the Bills to place him on IR last November after they signed him as a free agent following his release from the San Diego Chargers.
"Shawne has worked extremely hard, but unfortunately his Achilles flared back up and it doesn't appear that he will be able to return to the field anytime soon," Bills general manager Buddy Nix said in a statement released by the team Tuesday. "We felt it was in the best interest of our team and for Shawne to put him on IR."
After being bothered by a nagging shoulder injury for the past month, Merriman's Achilles suddenly became a problem on the Thursday before the Bills' 27-24 loss to the New York Giants. Merriman missed that game, but he expressed confidence that he'd be able to return and not miss significant time when the Bills returned from their bye week.
But Merriman didn't make as much progress from the injury as the Bills had hoped, leaving the team with a severe void in a pass rush that has generated just four sacks this season. Coach Chan Gailey and several players spoke last week about the need to pressure the quarterback to take the heat off Buffalo's defensive backfield, which already has allowed 300-plus passing yards three times this season.
Buffalo ranks 31st in total defense in the NFL.
A three-time Pro Bowl selection, Merriman finishes the season with nine tackles and one sack in five games. He had 43.5 sacks in 60 career games entering this season -- but just four sacks during the 2008 through 2010 seasons when his production was slowed by injuries.
Merriman missed most of the 2008 season after undergoing reconstructive knee surgery. Then, after sitting out most of the 2010 offseason workouts and part of training camp to protest his contract status, he was slowed by an Achilles' tendon injury and then a calf injury before being released mid-season by the Chargers.
The Associated Press contributed to this report.