For starters, let's forget about all the emotions and subplots that engulfed Peyton Manning's unlucky return to Indianapolis on Sunday night.

And to all the armchair analysts who have been working overtime since the Denver Broncos' 39-33 loss to the Colts: You're wasting the mental energy.

Only one factor is worth discussing this week. It fully explains why the Broncos had so much trouble at Indianapolis, why they couldn't break loose for so much of the night, and why they should be concerned right now about whether they can make it far into the postseason.

That factor: Denver's depleted, patchwork offensive line.

Back when training camp started, the Broncos felt justifiably confident about their projected line: tackles Ryan Clady and Orlando Franklin, guards Louis Vasquez and Zane Beadles, and center Dan Koppen (after returning starter J.D. Walton was hurt in June).

By Sunday night, only Beadles was still in place. Clady's gone for the year (foot), and Franklin (knee, ankle) won't return until November. Vasquez is filling in at right tackle, Chris Clark at left tackle, and the rest of the makeshift unit includes Manny Ramirez at center, Beadles and Chris Kuper at guard. With no quality backups for any of them.

That group couldn't stop the Colts from disrupting Manning's rhythm (until injuries affected Indy late). Their failures directly caused two of the most damaging plays: the sack-fumble-safety with Denver ahead 14-10, starting a 23-point run by the Colts to a 33-14 lead, and the interception near the end after Denver took over trailing 36-30 and needing one last score to complete a remarkable rally.

Those two plays had the biggest impact, but Denver's offensive line was overmatched all night, unable to open up any kind of consistent running game, and unable to stop the Colts from harassing and pressuring Manning, start to finish.

As a result, Manning couldn't depend on runner Knowshon Moreno in short-yardage situations, couldn't use play-action fakes and couldn't depend on the line to protect him enough for coverage to break down. Moreno was basically neutralized, Ronnie Hillman might have fumbled his way into oblivion, and Montee Ball was nowhere to be seen (though perhaps he'll get another shot now).

Sure, the Broncos still should have won, just as they should win others in the weeks ahead. But in tough road situations later in the regular season, they will need much more from their line than they got at Indy. Denver has gone from having a B-plus or even A-minus offensive line to more like a C-minus (or worse) group.

With Clady and Franklin at the tackles, Manning had ample time and the ground game worked. Losing the Pro Bowler Clady was costly enough, but when Franklin went down against Jacksonville, that was simply one injury too many.

What's the answer? Franklin surely won't play Sunday against Washington, which should be another shootout (with reverse angles, as Mike Shanahan returns on the opposite sideline). But then comes a well-timed off week for Franklin.

After that, if Franklin is fine and Vasquez moves back to his spot at right guard, perhaps Denver will have a better chance in its grueling four-game stretch that follows the bye week: at San Diego on Nov. 10, at home against Kansas City on Nov. 17, at New England on Nov. 24 and at Kansas City on Dec. 1.

Those four games will tell us whether these Broncos really are good enough to make a run at the Super Bowl. They clearly have most of the right ingredients, starting with Manning and his receivers. It's hard to fault the defense, either, though stupid penalties did hurt at times against the Colts.

At this point, it's just not realistic to call Denver a Super Bowl favorite anymore, now second in the AFC West behind revitalized, unbeaten Kansas City.

Not with that offensive line, and not with that four-game ordeal to come.