Without Brian Westbrook, the Philadelphia Eagles will likely have to rely heavily on Donovan McNabb as they try to get their season back on track this weekend.

The Chicago Bears aren't sure how much they can count on their quarterback.

With both teams describing it as a must-win game, the Eagles and Bears face off at Soldier Field on Sunday night, each trying to avoid a third straight loss.

Philadelphia (5-4) followed a 20-16 defeat against Dallas with a 31-23 loss at San Diego last Sunday. The Eagles were held to three field goals through the first three quarters before McNabb threw touchdowns to Jeremy Maclin and Brent Celek in the fourth quarter to cut the deficit to five points. The Chargers, though, tacked on a 29-yard field goal with 30 seconds remaining.

McNabb threw for a season-high 450 yards, going 35 of 55. He was intercepted in the end zone on the game's last play, though, and struggled repeatedly in the red zone.

"When you have those opportunities to score we have to pound it in there," McNabb said.

Despite the consecutive losses, McNabb and the Eagles are still in contention for a playoff spot, trailing NFC East-leading Dallas by one game.

McNabb will try to help Philadelphia make a play on first place, but he won't have Westbrook in the backfield. The two-time Pro Bowl running back was ruled out after suffering his second concussion in three weeks.

Westbrook was on the sidelines for the second half of last Sunday's game, and Philadelphia was held to a season-worst 29 yards rushing overall, averaging 2.2 yards per carry.

"It takes something away because you're talking about one of the best backs in the league and now we don't have him," fullback Leonard Weaver said. "We're going to have to step up. We've done it before."

LeSean McCoy will take over as the team's primary back. The rookie leads the Eagles with 353 yards and two touchdowns and now has the tough task of re-energizing the Eagles' struggling running game. They're averaging 102.1 yards this season, but have run for 65.8 in the four losses.

"I just want to help out the offense as much as possible," McCoy, the 21st pick in the second round of the 2009 draft, said. "I never really expected to play a big role like this. But I got drafted for a reason. I have my chance, my opportunity and I have to make the best of it."

With the running game shaky, the Eagles will turn to McNabb, who has been inconsistent this season. He recognizes the importance of Sunday night's game and believes despite Westbrook's injury, the team will come out fighting.

"This is a game that we need to win," McNabb told the Eagles' official Web site. "That's the way I'm approaching it and that's the way the other guys are approaching it as well."

As difficult as McNabb found it to get the Eagles into the end zone last weekend, his counterpart on the Bears is coming off an even worse performance. Jay Cutler threw a career-high five interceptions in Chicago's 10-6 loss at San Francisco on Nov. 12. The Bears (4-5) outgained the Niners 350-216 but settled for two field goals.

Cutler, who threw 18 interceptions while with Denver last season, already has a league-leading 17. All five picks last week were in San Francisco territory, including one to end the game with the Bears at the 49ers 12-yard line.

Chicago, though, isn't putting the blame solely on Cutler.

"It's different in each one," offensive coordinator Ron Turner said. "I look at three of them - and I'm not blaming anyone else, I'm just making a point it's a team game. I couldn't really say, 'Jay, you need to do something different on those plays.'"

Cutler has been forced to carry the offense because of an ineffective running game. Chicago is 30th in the NFL at 85.2 yards rushing per game. Matt Forte, who rushed for 1,238 yards as a rookie in 2008, has been held to 482 yards this season.

A division title is almost out of the question given that Minnesota has a four-game lead over Chicago in the NFC North. The Bears still believe a playoff berth as a wild-card team is possible, but they also recognize they will have to play much better down the stretch.

"We have no room for any more losses," defensive tackle Tommie Harris said. "If you lose, you're going to be hoping another team loses so you can get in. You don't want to do that. ... It is basically in our hands right now. We have to do a better job and everybody has to step up."

The Bears have won the last two meetings against the Eagles, including a 24-20 victory at home last season.