While Tim Tebow continues to defy his critics by turning the Denver Broncos into serious playoff contenders, the Chicago Bears' growing concerns at the quarterback position might end up costing them a spot in the postseason.

Tebow and the Broncos will try for a sixth consecutive victory Sunday as the visiting Bears seek to avoid a third straight defeat.

Denver (7-5) looked far from a playoff-caliber team when it sported a 1-4 record, but has won six of seven since Tebow replaced the since-departed Kyle Orton as starter Oct. 23. After coming back again last Sunday to win 35-32 at Minnesota, the Broncos -- winners of five straight -- moved into a tie with Oakland atop the AFC West.

Denver, which won 38-24 at Oakland on Nov. 6 to split the season series with the Raiders, currently owns the tiebreaker thanks to better divisional and conference records.

"It's been a fun ride," said linebacker Mario Haggan, who recorded 12 tackles and returned an interception for a touchdown against the Vikings. "This team is close, believes, has a lot of character, but we're not done."

The mobile Tebow proved last week that he can also win games with his arm, completing 10 of 15 attempts -- his first time this season completing more than 50 percent -- for a season-high 202 yards and two touchdowns. Those TD passes covered 62 yards to second-year receiver Demaryius Thomas, who had four receptions for a career-high 144 yards.

Tebow has completed just 47.5 percent of his passes in 2011, but he's thrown 10 touchdowns with just one interception and has the Broncos in position to win six straight for the first time since starting 6-0 in 2009.

Five of Denver's six wins with Tebow under center have involved second-half comebacks, including last Sunday when it trailed 22-14 late in the third quarter.

"I know I have been saying this for the past couple weeks but I'm so proud to have a team like this," said Tebow, who ran just four times for 13 yards at Minnesota. "When adversity hits and you're not doing good, most teams pull apart and they're not on the same page anymore. But our team grows closer together."

Denver's success has not solely been because of Tebow.

Running back Willis McGahee, who expects to play Sunday despite a knee injury, has rushed for 886 yards after toiling in Baltimore the previous three seasons in a crowded backfield with Ray Rice. He's run for 228 yards on 43 carries over the last two games, including 111 and a TD at Minnesota.

McGahee ended September averaging just 2.9 yards per carry, but has averaged 5.7 in eight games since the beginning of October.

Last weekend's defensive performance against the Vikings marked the first time in four games the Broncos allowed more than 13 points. Probably not coincidently, standout rookie linebacker Von Miller missed that game with a thumb injury.

Miller, the second overall pick in this year's draft who leads all rookies with 10 1/2 sacks, expects to play this Sunday.

That might not bode well for the Bears (7-5), who have dropped two in a row since Caleb Hanie was forced to replace the injured Jay Cutler at quarterback.

After a mediocre performance in 25-20 loss at Oakland in his first NFL start Nov. 7, Hanie was awful while going 11 of 24 for 133 yards with three interceptions in a 10-3 home defeat to Kansas City last Sunday. Hanie has posted a 48.3 passer rating in two starts while throwing two TDs and six interceptions, and been sacked 11 times.

"I've just got to do a better job getting us in the right position and getting the ball to our guys," said Hanie, who returns to the Mile High State, where he attended college at Colorado State.

Hanie likely must show some improvement if Chicago is to remain in playoff position.

The Bears currently own the fifth seed in the NFC, but play three of their final four games on the road, where they are 2-3. Making matters worse, they could be without running back Matt Forte for all of those contests.

The NFL leader with 1,487 scrimmage yards, Forte does not know how much time he will miss after suffering a sprained knee against the Chiefs.

"Everybody has to be up to the challenge and work through it," Forte said. "I think the guys on our team are able to work through that. They have a lot of resilience. I think they'll be fine. They're not really too down about it."

Short-yardage specialist Marion Barber, who has rushed for 281 yards and five TDs on 76 carries, is expected to get the bulk of the work in Forte's absence. Kahlil Bell, who gained 34 yards on four carries last weekend, also could see more time.

Chicago has won the last two meetings with the Broncos, including a 19-10 victory in its last visit to Denver in 2003. Devin Hester returned both a kickoff and punt for touchdowns in the Bears' 37-34 overtime home win in 2007.