Nobody said retuning to the Super Bowl was easy, but both defending conference champions are struggling more than expected this season. The banged-up Patriots are 3-3,which is what the Eagles would be if a blocked field goal last week had bounced toward a San Diego player instead of a Philadelphia defender with a clear path to the end zone.

EAGLES (4-2) AT BRONCOS (5-2)
(Sunday, 4 p.m.)

Last week, the Eagles shocked the NFL by keeping the league’s best running back, San Diego’s LaDainian Tomlinson, to just seven yards on the ground. The Broncos are also built around a great running game, so Philadelphia will probably try the same line of attack. But Denver has an advantage San Diego didn’t: a week to study last week’s game film.

If the Broncos cannot use the run to stay out of third-and-long situations, they’re in a heap of trouble. Denver has built a 5-2 record despite poor play on third downs, on offense as well as defense. Close wins kept this issue hidden until the Giants pulled back the curtain with Sunday’s last-minute win. In the fourth quarter, the Giants were 3-for-3 on third-down conversions; Denver was 0-for-3.

When the Broncos have a third down with three yards to go or less, they convert at the same rate as the league average. But when third down requires four or more yards, they convert just twothirds as often as other teams.

When the Broncos pass,watch for veteran receiver Rod Smith. Last year, the Eagles secondary, though otherwise strong, was unable to cover the opposition’s top receiver.This year is no different; remove the inept 49ers, and the Eagles are allowing top receivers to catch 75% of passes for an average of 94 yards a game.

In the off-season, Denver was ridiculed for bringing in a number of former Cleveland Browns to staff the defensive line, but the move has paid off and the Broncos are one of the league’s strongest defenses against the run. But that won’t matter much against the Eagles, who call running plays with the frequency of Haley’s comet.The line makeover has made less of an impact against the pass, and the Broncos rank last in the league when it comes to sacking opposing quarterbacks despite a strong year from holdover Trevor Pryce.

On the other hand, the Eagles’ passing game is not playing at the high level of seasons past. Philadelphia has built big numbers against poor pass defenses like San Francisco and Kansas City, but has finished below five net yards per pass in three of its six games this season. (The league average is six net yards per pass.)

If the game comes down to a lastminute field goal, Denver has a secret weapon on Philadelphia’s bench: kicker Jose Cortez. With the injured David Akers expected back soon, Cortez was signed as a kickoff specialist after being run out of Dallas on a rail. But since Akers won’t be back this week,the highly inaccurate Cortez will handle field goals as well, meaning Philadelphia shouldn’t trust any game-winning drive that doesn’t end with an Eagle in the end zone.

BILLS (3-4) AT PATRIOTS (3-3)
(Sunday, 8:30 p.m.)

There’s been a lot of talk this season about the possibility of a 7-9 team winning the NFC North, but that division currently has two teams at .500. The AFC East has just one: New England.

Of course, very few people expect New England to continue to play at a .500 pace.The Patriots’ early struggles have in large part been due to their schedule, which has led them to Carolina, Pittsburgh, Atlanta, and Denver in the last five weeks. They’ve also suffered from a torrent of injuries on both sides of the ball, including the loss of safety Rodney Harrison for the season and left tackle Matt Light for most of it.

A week off has given the wounded some rest, and many New England stars are expected to make their return,including defensive lineman Richard Seymour and running back Corey Dillon. But the return getting the most attention is that of linebacker Tedy Bruschi, who was recently cleared to play after making a remarkable recovery from a mild stroke suffered in February.

Cornerback Tyrone Poole was placed on injured reserve yesterday, leaving a roster vacancy that Bruschi could fill. It’ll likely be a game-day decision, but you know what coach Bill Belichick would prefer.Bruschi has been the leader of the Patriots defense for years, an undersized player with a natural instinct for the game that can’t be measured by a scale or a stopwatch, but is clear when tallying tackles and turnovers.

Should Bruschi make his return, he and Seymour should bolster New England’s defense against the talents of Buffalo running back Willis McGahee, but it won’t solve the glaring weaknesses in the secondary. Starting cornerback Randall Gay still isn’t healthy,and his backup,veteran cornerback Duane Starks, has been abysmal. Starks gives receivers too much cushion on short routes and is then left in the dust when receivers go deep.

But Buffalo has its own flaws and injuries.Taking advantage of Starks will be tough since a porous line has turned the deep pass into a rare occasion. Starting wideouts Eric Moulds and Lee Evans have caught only five passes over 15 yards after combining for 34 such passes last season.

On defense, Buffalo’s young cornerbacks can shut down the opposition’s best receiver, but have trouble stopping second and third options.That’s a major issue against a quarterback as skilled at spreading the ball as Tom Brady.Furthermore,the loss of middle linebacker Takeo Spikes to injury has crippled Buffalo’s run defense, which is allowing an NFL-worst 5.4 yards per carry. That means a happy return for Dillon if he is truly healthy, and a national spotlight for backup Patrick Pass if he is not.

The Patriots have had two weeks to rest and address their one clear weakness; the Bills have had one week to rest and address two clear weaknesses.That math says New England will return to the win column.

Mr. Schatz is the editor in chief of FootballOutsiders.com.