Denver Post sports writer Mike Klis posts his Broncos Mailbag on Wednesdays during the NFL season.

Pose a Broncos- or NFL-related question for the Broncos Mailbag.

Hey, Mike. I understand that there are a lot of reasons why this defense has improved tremendously. The biggest, in my opinion, has been a solid offense that is able to stay on or flip the field. If you HAD to select a No. 1 reason, what would it be?

—Mike, Rochester, N.Y.

To me, the No. 1 reason is the Broncos ability to put heat on the quarterback with a four-man rush. No blitzing needed. And late in games, when the Broncos are protecting a lead and the opposing offense is desperate and has no choice but to throw the ball down the field, only three pass rushers are required – Elvis Dumervil got his final-play sack on Philip Rivers off a three-man rush.

Miller, though, is the X factor. He’s the weapon that puts this defense over the top. When there’s heat on the quarterback, the likes of Tony Carter, Mike Adams and Chris Harris only have to cover their guys for 3 seconds, instead of 5.

One of the underrated keys for Miller, by the way, is the creative ways defensive coordinator Jack Del Rio moves him around. It’s tough for an offense to put a tight end or back on Miller’s side if they’re not sure from what side he’s going to pass rush. Miller’s flexibility in where he rushes from is part of what makes him exceptional. Some pass rushers only like to line up on one side and predictability is what makes it easier for opposing game plans to counter.

The ability to rush the passer with only four guys was a big reason why the New York Giants have twice got the better of the mighty New England Patriots’ offense in their past two Super Bowl meetings. When a defense has to blitz to reach the quarterback or stop the run, it’s exposed in other areas.

I’d like to encourage everyone writing in Denver as the AFC West champions to use pencil. Just a few years ago, Denver had a three-game lead with three to play, and the Broncos choked it away in embarrassing fashion. Granted, this team is a different beast with Peyton Manning, Von Miller and company. Just saying that the large woman in the Viking hat and braids is still doing vocal exercises, not singing.

—Ryan, Denver

Sorry, but the AFC West title can be written in indelible ink. Ordinarily, your caution is prudent. But have you seen the other three teams in this division? The Chargers aren’t going 5-1 in their final six games to finish 9-7. The best they can do is 8-8. Even if the Broncos collapse and finish 8-8, they would have the tiebreaker.

And it’s impossible for the Broncos to go from 7-3 to 8-8 with two remaining games against 1-9 Kansas City and a home game against 2-8 Cleveland. It just can’t be done.

So the AFC West is in the bag, Ryan. Tell you what, if the Broncos don’t win the West, I’ll wear a Vikings hat and braids on all playoff dates in January.

Who is the more valuable receiver to the Broncos: Demaryius Thomas (more talent) or Eric Decker (more guts)?

—Greg Price, South Dakota

You say Decker has more guts? Boy, has his perception come a long way since “The Slide.” I’ll agree that Decker has been a tackling-busting machine. He has gone above and beyond proving that “The Slide” against Houston was an out of character, if understandable (he was gassed) maneuver.

Much as you hate to bust a tandem that’s been so productive as a duo, Thomas is the freak here. Decker may well be a top 25 NFL receiver but Thomas is a top 5.

With apologies to Rod Smith’s remarkable production and Brandon Marshall’s talent, Thomas has a chance to become the best receiver in Broncos history. At 6-foot-3, 230 pounds, Thomas has Marshall’s size but considerably more get-open speed downfield. Marshall has had one 200-yard game in his career and he needed an NFL-record 21 catches to get there. Thomas had 204 yards on just four catches – including the game-winner in a playoff game. The next playoff game Marshall plays in will be his first.

I also think Thomas has better hands than Marshall.

The top two NFL receivers are Calvin Johnson and A.J. Green. You can argue about whether third best is Larry Fitzgerald, Andre Johnson, Roddy White, Reggie Wayne, Victor Cruz or Percy Harvin. But I think it’s Thomas because of size, speed, production — and youth. He doesn’t turn 25 until Christmas Day.

The key for Thomas, though, is staying healthy. He may be young but his body has already absorbed its fair share of trauma. It’s easy to be relatively healthy when you’re 25. How about when he’s 34 like Reggie Wayne?

Looks like we could go deep into the playoffs, but I’m concerned with our turnovers — the number of them and the fact that when we fumble the ball it’s almost a given the other team recovers it. How do you stop the turnovers? What do the coaches do to improve in this area?

—Dave C., Irvine, Calif.

Specifically, the problem has been fumbles. The Broncos have lost 13 fumbles through 10 games. Only their opponent this week, the 1-9 Kansas City Chiefs, have more with 16 lost fumbles.

When you have nearly twice as many fumbles as interceptions (7), it’s a concern. The Broncos have worked on ball security and recovering fumbles during practice in recent weeks. Scout teamers have been told to try and strip the ball. Fumble recovery drills have been installed during the position periods.

Right now, the player who makes Broncos fans hold their breath is returner Trindon Holliday. He’s a breath-taking returner but he’s also a heart-stopping bobbler. It’s clear opponents are making a concerted effort to try and strip him of the ball. John Fox is concerned enough to use Jim Leonhard as his designated fair catcher.

I love having Manning, but I’m also thinking of the future. I’m really hoping that Brock Osweiler is absorbing everything he can from Manning, but I never see him on the sideline huddles when Peyton calls the offense together. How much is Osweiler shadowing Manning and how much is he trying to take all this in? We have an amazing window with Peyton, and I’d hate to see that go to waste.

—Everett, Vancouver, Wash.

I have often seen Osweiler listening in on Manning during those offensive “de-briefing” sessions between possessions. The kid does work. And he is smart. He does understand the opportunity he has in learning from the most cerebral quarterback who ever played.

But at some point, Osweiler will get antsy. If all goes well with the Broncos, they will have clinched a No. 2 playoff seed entering their final game of the season and Osweiler will get to play against the Chiefs.

The Broncos drafted Osweiler figuring he would sit for three years. If they miscalculated and it appears Manning can compete for the Super Bowl at 39 and 40 years old, and Osweiler becomes a free agent after his fourth year without getting a chance to play, then yes, he will have been a wasted pick.

But think about it, Everett: If Manning brings the Broncos to the playoffs in his first four seasons, plays in two Super Bowls, and wins one, then the Osweiler pick will be criticized. But if there’s more Osweiler than Manning in the next four years, then the Broncos’ master plan will have gone awry.

I think what the Broncos have here is a double-insurance policy at quarterback where one protects the other.

I’ve noticed a lot of talk about Von Miller being a leading candidate for defensive player of the year. The main praises are tackles for loss and number of sacks. Yet Wesley Woodyard is leading the team in tackles. What else will voters look at to determine if Miller should win? Sacks seem like a glamour number that only tells part of the story.

—David, Franklin, Tenn.

Sacks and tackles for loss aren’t just glamour plays. They’re impactful plays. Difference makers. It is a little different from our high school days, David. In high school, or Pop Warner (which wasn’t an option in my day), the best player always made all the tackles.

In the NFL, defense is more team-based. Linebackers better lead the team in tackles because the way the system works, the big boys up front eat up all the blockers, leaving the second-level players to get the ball carrier. In theory, anyway.

And that’s only the theory in stopping the run. The key to playing defense in today’s NFL is stopping the pass. That’s why pass rushers and cornerbacks get all the money and fame.

What’s worth noting is Miller was NFL Defensive Rookie of the Year last season even though fellow rookie Aldon Smith of San Francisco had more sacks (14 to 11.5). And this year, Miller has emerged as a top Defensive Player of the Year candidate even tough, again, Smith has more sacks (15 to 13).

Some of this can be attributed to Miller also dominating with his league-leading tackles for loss (44 the past two years compared to 28 by Smith). And some of this may be that Miller has the type of innocent, fun-loving, yet professional personality voters like to see in their star players. Not that Smith isn’t a great guy. I don’t know him. But I do know people seem to like Von.

When will we get to see Denver play in some throwback jerseys with the old Denver “D” and the fighting horse coming out center?

—Trevo, Lexington, Ky.

Funny, I was just talking with Broncos president Joe Ellis about this subject following the Broncos’ “all blue” victory Sunday against San Diego. Ellis is acutally an advocate of the all orange uniform fromt he 1960s with the donkey logo on the helmet! (Circa 1962-1963.) However, due to deadlines, the Broncos probably won’t go throwback in 2013. Maybe 2014.

Personally, I haven’t seen many throwbacks that I like generally. There’s a reason why they’re suitable for modern fashion. They’re not throwbacks, so much as throwaways.

Pose a Broncos- or NFL-related question for the Broncos Mailbag. Listen to Mike Klis on “Klis’ Korner” at 5 p.m. Monday, Wednesday and Friday as well as 12:30 p.m. Tuesday and Thursday on 102.3 FM ESPN.