The Buffalo Bills' undefeated start was derailed by the NFL's second-highest scoring team in their latest game, as the previously stout Bills' defense surrendered 41 points in a blowout loss.

With a bye week to regroup, Buffalo now has the league's highest-scoring club in its way.

The AFC East-leading Bills will try to get back on track Sunday when they return home for a date with the high-powered San Diego Chargers, who are looking for their fourth win in five games.

Buffalo (4-1) got off to a surprising 4-0 start thanks to the efficient play of quarterback Trent Edwards and a defense that was giving up just 15.6 points per game. But on Oct. 5 at Arizona, Edwards was knocked out of the game with a concussion on the third play of the game, and Buffalo's defense couldn't step up in an ugly 41-17 loss.

Backup J.P. Losman turned the ball over three times and the Bills had four turnovers in all.

"It was bad. We just played bad in every phase of the game," safety Donte Whitner said. "We know that we can't play that way any more. And I don't think you'll see that again."

The Bills should get some help against San Diego (3-3). Edwards, who's completed 66.4 percent of his passes and has a 93.9 passer rating, returned to practice this week and says he'll play Sunday.

"I'm happy and excited that I'm out there with my teammates and not on the couch at my house," Edwards told the team's official Web site. "It's a much better feeling coming into work feeling healthy and feeling good coming off a bye week, and hopefully I'll have a big game on Sunday for us."

Edwards and the Bills may need to have a big day to keep up with the Chargers. San Diego is averaging 29.7 points, tops in the NFL, and is coming off a 30-10 blowout of New England in Week 6.

With LaDainian Tomlinson hobbled by a toe injury that's limited his effectiveness, the Chargers have put the game on Philip Rivers' shoulders, and the fifth-year quarterback has come through. Rivers is the league's highest-rated passer (109.4) and is tied for the NFL lead with 14 touchdown passes.

Rivers threw for 306 yards and three scores in the win over the Patriots, the fourth time this season he's tossed three touchdowns.

"I think it was obviously good to play well," Rivers told the Chargers' official Web site. "It was important mainly just to get a win. I think it's like this not just in offensive consistency or anything as a team, it's a week-to-week thing. You've got to gear up and do it again."

If San Diego plans on winning the AFC West, and perhaps making a return trip to the conference championship game, it'll likely need to start running the ball better. The Chargers have been one of the NFL's top 10 rushing teams in each of the last six seasons, but they're tied for 21st so far this season with just 98.5 ypg.

Tomlinson is averaging just 3.4 yards per carry in his last two games and he hasn't scored. The Bills are 18th in the NFL in rush defense, allowing 114.2 ypg.

"We've been patient and hopefully a really big day is right around the corner," left tackle Marcus McNeill said. "We've got a coach that's committed to the run and a runner who's the best. We'll get there."

Buffalo also has a running game that hasn't lived up to expectations. Marshawn Lynch averaged 4.0 yards per carry as a rookie last season and seemed to be a candidate for a breakout season, but he's struggled to get going thus far. Lynch had three 100-yard games in his final six in 2007, but doesn't have one yet in 2008. He's averaging just 3.5 ypc and hasn't scored in his last two games.

"We're a work in progress," Bills right tackle Langston Walker said. "We're running more in the red zone, which was an emphasis from our coaches. We're going to re-evaluate things ... and see if we can change things and make things better."

In addition to a healthy Edwards, one big boost for the Bills could come in the return game. The speedy Roscoe Parrish, who also stretches the field for Edwards in the passing game, is expected back after missing the past two games while recovering from thumb surgery.

Parrish returned a punt for a touchdown in the Bills' Week 1 win over Seattle, and caught a touchdown pass in their Week 3 win over Oakland.

The Bills are 13-6 following a bye, and haven't lost after an off week since 2004. They're just 4-10 all-time against the Chargers.