Some of the more intriguing matchups of the season should present themselves Sunday in Denver when the Vikings' Adrian Peterson-driven power running game tries to neutralize a quarterback-breaking defense while minimizing Peyton Manning's time of possession.

For a closer look at the Broncos, we turned to veteran NFL reporter Jeff Legwold, who covers the team for ESPN. He has covered the league for more than two decades, arriving in Denver in 2009 to cover the Broncos for the Denver Post. Legwold also is on the Pro Football Hall of Fame Board of Selectors.

MC: I know it has become popular to say Peyton Manning's arm is shot, but from this viewpoint it appears the offensive line and a new system that's still developing are more to blame for any struggles offensively. How much of those struggles do you attribute to an entirely new offensive line, Gary Kubiak's new system and, finally, Manning?

JL: The Broncos rolled the dice a bit by not signing guard Evan Mathis until late August, because that meant they didn't start their current offensive line in a game until the regular-season opener. The zone scheme relies on communication and the ability to move as a group and not leave any gaps, so they're still working out those kinds of issues, issues most teams get figured out in training camp. As far as Manning, much of the conversation is centered around how he "looks" rather than the results. Some of it is the standard he has set, some of it is what people are used to seeing and some of it is just the fact he's 39 years old and has adjusted his game to reflect four neck surgeries as well as the number of birthdays he's had. In the end, he's starting to get dialed in and if Emmanuel Sanders doesn't have the ball punched out of his hands on a deep throw in Kansas City, Manning would be coming off back-to-back 300-yard games with five touchdowns combined. When he has room to climb the pocket — his throwing motion is more lower-body pronounced post-neck surgery — he can still move the ball to all parts of the field. He gets in trouble when he throws falling backward or with his legs in a straddle position. If he gets business class leg room, he will find the receivers.

MC: Speaking of the offensive line, for lack of a better way to put it, what the heck happened? A torn ACL for the left tackle in OTAs? Trading the center on draft day? Letting the left guard join a division opponent via free agency? Are we missing anything and are these things the team will live to regret or can this group rebound from three weeks of porous pass protection and the league's worst average per carry?

JL: The Broncos' decision-makers, led by executive VP of football operations/general manager John Elway, were decidedly unhappy with both how the offensive line played and how it was coached in 2014. And the game video shows Manning covered up a lot of flaws — he was only sacked 17 times — even as the Broncos running backs were hit at, or behind the line of scrimmage, on a third of the team's carries in '14. So, a makeover was coming with the new coaching staff and the new, more movement-dependent scheme and coach Gary Kubiak was intent on having a "young group we can keep together for a little while," so this is kind of the investment season in that strategy. The risk was in trying so many combinations through the offseason program and training camp. Originally, Kubiak said many times in the offseason, the Broncos hoped to have the personnel selected in the offensive line by the start of training camp, but they eventually kept trying different groupings, up until they signed Mathis in late August. They like the group they have and now, it's a matter if they can settle in or not. Their issues haven't consistently been one player or one thing, they have been a combination of assignment issues on particular plays or the learning curve in a new system that is very different from the one they played previously. They easily had their best outing Sunday night in Detroit while both Kubiak and Manning believe they have found a little something in the pistol formation. The Broncos protected far better and Manning was 11-of-13 for 118 yards in the 29 snaps they were in the pistol against the Lions.

MC: The Broncos look like they not only have the best edge rushing combo, but also the best trio of cornerbacks. Is this group playing as well as you've seen it play and is defensive coordinator Wade Phillips doing anything differently with the defense this year?

JL: With the proverbial still-a-long-way-to-go caveat right here, this defense has the potential to be one of the three best defenses for teams I've covered in my career with the '92 Steelers (No. 2 in points allowed, No. 1 in takeaways) and the '00 Titans (No. 1 in total defense, No. 2 in sacks, No. 2 in points allowed — Ravens set record for 16-game season and were No. 1 in points allowed). The Broncos largely have the same personnel they had a year ago when they were No. 3 in total defense, No. 16-T in points allowed, but Phillips has turned them loose, with plenty of man coverage and a mix-and-match approach in the rush where there the Broncos have largely rushed four players much of the time. It's just Phillips will bring the four from anywhere in the formation with Ware and Miller usually leading the way. But the Broncos use a lot of personnel as well. In the win over the Lions, 20 different players played at least two snaps in the game on defense. That includes a player like outside linebacker Shaquil Barrett, who spells Ware or Miller at times, who played just 10 plays against the Lions and had a sack and a forced fumble. In the end, though, it all starts with the fact the Broncos have elite coverage players — Phillips has called Aqib Talib and Chris Harris Jr. the best cornerback tandem "I've ever had" and Bradley Roby would certainly start for many teams — to go with two elite rushers. It is hard to assemble that in the salary cap era.

MC: For the Vikings to have any real chance of competing, they'll have to run the ball as well as they have the past two weeks (73 carries, 362 yards, five TDs, 5.0 average). How well do the Broncos stop the run and how do you think they'll match up with Adrian Peterson?

JL: The Broncos are so aggressive, there is always potential for them to get caught over-pursuing, but they have surrendered just four runs of over 10 yards in their three games and one run of over 13 yards — all by Jamaal Charles. They can run plays down — especially their inside linebackers Brandon Marshall and Danny Trevathan — and have largely controlled the line of scrimmage to this point. One thing that has helped them is they have athletic safeties who are physical at the line of scrimmage. So, because of that the Broncos have limited the damage teams have done in the run game when the offenses choose to try to make them lighter on defense, by making the Broncos go to a nickel or dime look and then running at that lighter personnel grouping. But the Broncos will then use safety T.J. Ward or safety David Bruton Jr. at what is essentially a weak-side linebacker. In recent seasons teams have repeatedly succeeded in pounding away in the run game on the Broncos' nickel and dime looks, especially in the matchups the Broncos have had with the Patriots. But that is another thing this Broncos defense has done better as well."

MC: The Vikings only come to Denver every eight years, so, naturally, the altitude question was asked early this week. Coach Mike Zimmer said according to the scientific data he's seen, the altitude has no effect on players once they've been in Denver for 24 hours. In your experience and coverage of the team over the years, what trend, if any, have you noticed or uncovered? Is there something to it or is it just hype that's enhanced by good teams and a loud stadium?

JL: Just from living here, the biggest issue is hydration — doctors and climbing experts will tell you that people perspire and exhale twice as much moisture at 5,500 to 6,000 feet as they do at sea level. Couple that with fact it's low humidity, people have to drink more at altitude — Denver is essentially high desert — and there are times when teams don't hydrate enough during the week. And then they get here for their 36-hour stay and they find themselves having cramping issues. "No effect" is strong language, but likely true in terms of getting a headache, etc…, which some people will experience when they arrive here and then immediately try to go from the airport up past 10,000 feet into the mountains or do heavy activity in the Denver-area. Elite athletes will always adapt quickly in terms of performance, but it is different to exercise at altitude — less oxygen — and it will be evident fairly quickly if the Vikings have handled the hydration issues.