The Broncos have managed to go undefeated heading into Week 8, but to the surprise of many it is not because of their offense.

If the Broncos hope to remain spotless, it will be the defense that needs to continue to step up, as there is very little reason to believe that Peyton Manning will be able to turn things around. Manning is 31st in the NFL with a passer rating of 72.5. The veteran quarterback is also tied with Philly's Sam Bradford for the league lead in interceptions with 10, despite only playing six games so far this season.

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Nearing the halfway point of the season, it's going to be hard to imagine those ranks getting significantly better. And It gets deeper than just the stats for Manning. His numbers at face value are clearly atrocious, but other metrics are not in his favor.

The offensive line for the Broncos has struggled mightily, with SB Nation saying, statistically, it is the team's biggest negative. They have allowed Manning to get sacked 12 times, which ranks among the top half in the NFL.

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With a poor offensive line also comes a poor running game. C.J. Anderson, a player many fans and experts had going in the first round of their fantasy drafts, is 48th in the NFL in yards with just 180 and he's averaging a paltry 2.7 yards per carry. Anderson's poor play has left the Broncos sitting 30th in the league with only 510 rushing yards on the season.

When you combine a poor offensive line and a poor running game, teams know you're going to need to throw the ball and fast. Manning doesn't have the time to get balls to his talented receivers down the field and he certainly doesn't have the mobility to make plays with a broken pocket.

While the Broncos can continue to succeed thanks to their defense, there is very little reason to believe that Manning and the offense will turn things around this season.

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