September 17, 2015. That was the last time the Denver Broncos defeated the Kansas City Chiefs.

Been some lean, dark days in Denver since the Broncos hoisted the Lombardi Trophy following Super Bowl 50. After winning five-straight Division titles, the AFC West has since belonged to the Chiefs, with the Broncos struggling to compete while fielding a comedy of musical chairs at head coach and quarterback.

Fans hoped that the unfortunate losing streak vs. the Chiefs would come to an end earlier this year with a new head coach and a former Super Bowl MVP at quarterback. But even with Patrick Mahomes going down with a dislocated knee in the second quarter of the rivals' Week 7 tilt, the Chiefs boat-raced the Broncos at Empower Field, extending their winning streak to eight consecutive games.

However, with the upstart rookie Drew Lock having so recently gone into NRG Stadium and shellacked the playoff-caliber Houston Texans 38-24, making NFL history along the way, fans feel like for once in a long time, momentum (and perhaps the law of averages) is on Denver's side.

Lock grew up in Lee's Summit, MO, about 22 miles outside of Kansas City. So this coming week's road trip to Arrowhead Stadium is very much a homecoming of sorts.

Lock vs. Mahomes. This week's matchup could be a preview of the AFC West's marquee head-to-head QB duel for years to come.

If the Broncos are going to come out on top, it'll take another sensational performance by Lock, no doubt, but Coach Fangio is looking for something very specific in his expectations for his rookie QB in Week 15.

“Hopefully more of the same," Fangio said on Monday from Broncos HQ. "Maybe be clean and not throw a pick this game."

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Anytime you go against an elite team, the margin of error is slim. Lock is fortunate the Broncos defense was able to bail him out of the third quarter interception he threw in his debut back in Week 13, and equally so that his team had a multi-score lead when he threw his second pick in Houston the following game.

Still, Lock's 5-to-2 TD-to-INT ratio is a healthy one. But if he's going to, as Coach Fangio calls it, play a "clean game", this week in Arrowhead would be the most fortuitous time to do so.

There's a fine line between being protecting the ball and being timid. Lock has shown a propensity through two starts of being fearless when throwing vertically. He's been the impetus for some big passing plays downfield. And the Broncos recognize that.

"Really, he’s just progressing the way we had hoped—better in Week 2 than he was in Week 1," Fangio said on Monday. "I thought he felt comfortable out there. I think it was good that we got him his first start at home so when he got his first start on the road, it wasn’t his overall first start. We have to go play another really good team this week. He’s going to have to deal with the hometown stuff that you guys and they will want to write about. I feel good where he’s at.”

As for whether Lock's performance through his first two starts has been authoritative enough to cement him as the Broncos bonafide long-term quarterback, publicly, Fangio pumped the brakes. Privately, my bet is that the Broncos are thrilled with Lock's emergence.

“I don’t know. It’s two games," Fangio said. "Who’s long-term right now? He’s doing good. He’s done well for two games. That’s about all it is.”

So far, the Broncos' plan for Lock has paid dividends. The Broncos had six different starting quarterbacks between Peyton Manning's retirement and Lock's ascension. Being that he's the No. 7 QB to start for the Broncos post-Super Bowl 50, if that's not an auspicious omen in the Mile High City, I don't know what is.

Follow Chad on Twitter @ChadNJensen and @MileHighHuddle.