SD at BUF: 3 things you need to know

The Buffalo Bills hope to remain undefeated when they host the San Diego Chargers on Sunday. 

Here are three things you need to know:

Ground-and-pound or aerial assault?

While they won't be matched up simultaneously (keeping in mind the small sample size), this game will pit a top-ten rushing attack against a top-ten passing unit.

The Bills averaged 153 yards on the ground through their first two games, good for seventh in the NFL. C.J. Spiller is averaging 61 yards per game on an average of 13.5 carries. Fred Jackson's 85 rushing yards on 19 total carries have taken pressure off quarterback E.J. Manuel, who has the Bills only rushing touchdown.

The Chargers are averaging 257 passing yards though their first two games, which ranks eighth in the league. Quarterback Philip Rivers threw for 287 yards, three touchdowns and no interceptions in last Sunday's upset win over the Super Bowl-champion Seattle Seahawks.

Ryan Mathews expected to miss 4-to-5 weeks

Chargers running back Ryan Mathews suffered a sprained MCL late in the win over Seattle, and a MRI on Monday revealed could be sidelined for over a month.

Mathews rushed for 71 yards and a touchdown on 23 carries over the first two games before exiting Sunday, adding four receptions for 46 yards.

The Chargers offense should rely heavily on the passing game in his absence, which could make the offensive unit predictable and one-dimensional.

Bills run defense will test Chargers repacements

Former Indianapolis Colts rusher Donald Brown and versatile back Danny Woodhead will be called upon to pick up the slack for San Diego with Mathews on the mend, but they'll be in tough against the Bills' run defense.

Buffalo has held opponents (the Chicago Bears and Miami Dolphins) to 83 rushing yards per game, a figure that ranks them 5th in the NFL.

The Bills kept Bears tailback Matt Forte out of the end zone in the season opener -- limiting the Pro Bowler to 82 yards on the ground -- and forced him into the passing game where he racked up 87 yards on eight catches.

Brown is in his sixth NFL campaign but has never rushed for more than 645 yards in a season. Woodhead is an effective complimentary back but more useful as a receiver, hauling in 76 catches for 605 yards in the Chargers offense last season. Whether it's Brown or Woodhead who shoulders the load, they face a stiff test at Ralph Wilson Stadium.