DENVER (AP) Not so long ago, Peyton Manning had the Denver Broncos offense scoring at a record-setting clip. Those days are gone.

Now, it's the defense pulling most of the weight and even providing some scoring.

Six games into the season, the Broncos `D' is drawing some comparisons, however preliminary, to some of the best. Some look at the statistics - Denver ranks in the top three in eight defensive categories - and immediately start bringing up the 1985 Bears. But that team's offense, led by Jim McMahon and Walter Payton, was ranked second.

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A more apt comparison might be the 2000 Ravens, whose top-ranked defense propped up an offense that often went nowhere. The Ravens defenders enjoyed their role.

''There was really no frustration on our part, as a defense,'' said Peter Boulware, the four-time Pro Bowl linebacker who played alongside Ray Lewis. ''We were a team that wanted to do whatever it took to win the games. As a defensive player, we liked the game being on us.''

The 2000 Ravens still own the record for fewest points (165) and fewest rushing yards (970) allowed in a 16-game season.

In five straight games that season, the Baltimore offense failed to score a single touchdown and the Ravens still won two of those games.

When the season was over, the Ravens defense ranked first in yards allowed while the offense ranked 14th in total gained.

At first, Boulware recalls, there were some identity issues for the Ravens. How could a team with Priest Holmes and Shannon Sharpe, and coached by offense-minded Brian Billick, rely so heavily on defense? Eventually, Billick and the rest stopped fighting it.

''Once Brian squared it away with the team, and said, `You know what, we have a great defense, the objective is to win,' everyone got on board,'' Boulware said. ''We went heavy run, very conservative pass, punt the ball and play field position. We did not try to reinvent that.''

The Broncos head into their bye week at 6-0 but with lots of issues on offense.

Clearly not comfortable in coach Gary Kubiak's new system, Manning is struggling. He has seven touchdown passes and 10 interceptions, three of which have been returned for scores. The running game is worse. Kubiak wanted to take pressure off his 39-year-old quarterback with a better ground game, but the Broncos are ranked 30th in rushing at only 85 yards per game.

Overall, the offense is ranked 29th, while the defense leads the league in sacks and is in the top five in yards allowed, interceptions and fumble recoveries. The Broncos joined the 2013 Chiefs as only the second team this century to record 17 takeaways and 26 sacks over the first six games.

In all six games, the defense has made a sack or forced a turnover in the half of the fourth quarter or overtime to either save the game or win it. Denver's defense has scored a touchdown in four of six games.

''We're able to produce. That gives our team the best chance to win,'' safety David Bruton said. ''If we don't produce those numbers, don't play how we've been playing, who knows - we could easily be 0-6. We're 6-0 and have a long season to go and a lot more work to do.''

The question is how much Kubiak wants to mess with that formula. Denver's schedule is daunting. Green Bay is next, and there are also games against New England, Cincinnati and Pittsburgh.

''I would never do anything that I don't think is best for the quarterback,'' Kubiak said. ''That's my plan every day I go to work.''

If his defense keeps playing like this, he may want to take a page out of the 2000 Ravens playbook.

''We felt like it was OK for us to score 17 points to win a ballgame,'' Boulware said. ''It was OK for us not to put up thousands of yards. Once that got resolved in our minds, we really felt unstoppable.''