ORCHARD PARK - After a lightning-quick start, the luster of the Bills defense has worn off over the past few weeks.

Failing to generate much pressure on the opposing quarterback and unable to create turnovers, Buffalo's defense has helped keep the team mired in a sluggish 1-3 stretch over the last four games.

Turning things around will be even greater challenge this week at New England (5-3), as starting strong safety Donte Whitner will join defensive end Aaron Schobel (foot) on the sidelines because of a separated shoulder.

In addition, coach Dick Jauron said Thursday that nickelback Ashton Youboty has plantar fasciitis, making it highly unlikely he'll play against the Patriots.

“It is difficult, and it doesn't make it any easier,” defensive end Chris Kelsay said. “It's something that we have to rally together and try to fill those voids as best as possible. We can't give up, and we can't start pointing fingers.”

Buffalo's (5-3) defense has had a rough go since the team's 4-0 start. Over the first four games, they accumulated 10 sacks, including a season-high five in an opening-week 34-10 blowout over Seattle. But during the past four games, they've dropped the quarterback for a loss just three times, including once in Buffalo's three losses.

The Bills ugly minus-5 turnover ratio is also sixth-worst in the league.

“It's all about execution,” Kelsay said. “You have to make sure you're accountable to your teammates and not do anyone else's job.”

Part of the problem is that Schobel, their best pass rusher, hasn't played since injuring his left foot in the loss to Arizona on Oct. 5.

Another has been a banged-up secondary. Top cornerback Terrence McGee missed a pair of games because of a knee injury.

The defensive backfield will take another hit this week when Whitner watches after being hurt late in Buffalo's loss to the New York Jets on Sunday.

“It's going to be different,” said cornerback Jabari Greer, who has been one of the few bright spots on the defense with two interceptions returned for touchdowns this season. “Donte is the captain and leader on our defense, and is someone that is inspirational and motivational.”

Youboty, who's missed the past three games, will be replaced by either Leodis McKelvin or Reggie Corner, both rookies.

“They've got good skills,” defensive coordinator Perry Fewell said. “We're doing things that they can do, so if they have to play in the football game, I expect them to step up and play well.”

The Bills will have their hands full against a Patriots team that is hitting its stride. New England has accumulated an average of over 360 yards in its past three games.

“They have an explosive offense,” said Bryan Scott, who'll replace Whitner. “They have great receivers, great running backs and a great tight end, so it is a huge challenge for us.”