ENGLEWOOD, Colo. -- The Denver Broncos and Kansas City Chiefs have played 122 times over the past six decades or so.

But none mattered to the current state of the rivalry more than Dec. 31, 2017. On a cloudy, 17-degree day in Denver, a 22-year-old Patrick Mahomes made his first NFL start at quarterback for the Chiefs.

And while Mahomes threw his first career interception (Darian Stewart made the play) and did not have his first 300-yard passing performance (he finished with 284 yards), the Chiefs still won 27-24. Even then, it was abundantly clear young Mr. Mahomes was going to be a significant issue for all things Broncos for years to come.

Especially since the Broncos' own first-round quarterback that day -- Paxton Lynch -- threw two interceptions and was sacked five times in the last of his four career starts for the Broncos. That's known as one football ship passing another -- like at Cigarette boat speed -- in the night.

It was, at the time, the Chiefs' fifth consecutive win over the Broncos, a streak that began in Peyton Manning's last start against Kansas City, a dismal day for the Broncos as an injured Manning completed 5 of 20 passes with four interceptions before being pulled.

The win streak is now 11 for the Chiefs. But the current Broncos -- these roller-coaster ridin', quirky, injury-ravaged Broncos -- will arrive in Arrowhead Stadium on Sunday at 6-5 with the chance to play the Chiefs (7-4) for first place in the AFC West (8:20 p.m. ET, NBC). The division race isn't anywhere close to being decided by whatever happens Sunday, but a significant game, in December, against the Chiefs, has been a long time coming.

"For us, it means a lot," safety Justin Simmons said. "It's going to be a really good game. Another statement game. No matter what happens, we have to find a way to leave Arrowhead with a win."

Mahomes is now 26 and in his fifth NFL season. He has been a Super Bowl MVP, a league MVP and has never lost to the Broncos. The Chiefs have won when he's had a great day (four touchdown passes in 2018 to go with a 340-yard). They've won when he's had a workmanlike day (200 yards passing and one touchdown in a 27-point win last season), and they've won when he has left the game with an injury (hello, Matt Moore, in 2019).

During the streak, former Chiefs nose tackle Dontari Poe has the same number of touchdown passes -- one, in one of the Chiefs' 2016 wins -- as quarterback Brock Osweiler in his one Broncos start against the Chiefs and more than quarterback Joe Flacco had in his.

"Yeah. It's extremely personal," Simmons said earlier this week of losing to the Chiefs. "... You have to go deal with it. No one cares what it looks like. All anyone cares about is that win-loss column. That's what we have to do -- find a way to win."

Today is Dec. 1. And when that page flips on the calendar, any Broncos trip to Kansas City has usually gone down about as well as undercooked barbecue, even as team after team, player after player and coach after coach have said that stuff really doesn't matter.

The Broncos are 3-19 in December at Kansas City dating back to both teams' AFL tenures. They are 3-16 at Arrowhead.

Manning only started one December game in Arrowhead for the Broncos (a win), but Elway started seven of them during his Hall of Fame career and Denver went 1-6 in those games, so bust out the slide rules to figure that out, because something's going on.

Broncos coach Vic Fangio has lauded the willingness of the current Broncos to get off the mat a few times already this season, including Sunday's win over the Los Angeles Chargers: "We're excited to be on the hunt -- this is a resilient group." In the end, perhaps the team's rookies, who have no history in the rivalry and an increasing role in the fortunes of the current Broncos, can simply play because they don't know what they don't know. That might be the only way to end the skid.

"It means a lot," said cornerback Pat Surtain II when asked earlier this week about playing the Chiefs for a chance at the division lead. "We feel like as a whole rookie class, we got drafted to this team to play in big-time games, especially at the end of the season in big-time division matchups. We know that these are big, key games going forward toward our playoff run."