For the entire 21st century — all thirteen years of it — many folks in Denver with a sense of history have decried the replacement of venerable Mile High Stadium with its thoroughly modern, multi-revenue-streamed, marble-clad successor.

Sure, it allowed the Broncos to remain economically competitive with their peers, all of which were doing the same thing, but the thunder was gone, the shake, rattle and roll, the whole erector set bouncing thing that freaked out novice national broadcasters every time.

Sunday night, it was back. Well, maybe not the erector set bounce, but everything else. The 77,076 who packed the place, many of whom came early and spent the cool, sunny afternoon in sweet anticipation, gave the visiting Kansas City Chiefs a preview of the fourth quarter in the first, roaring and stomping from their very first snap, which, not coincidentally, turned into a penalty for a false start.

In a battle for first place between a highly-admired 8-1 team and a somewhat less admired 9-0 team, the 8-1 team not only won, it also kept its quarterback upright throughout, no small feat against a defense that had sacked opposing quarterbacks more often than any other.

For the Broncos, keeping Peyton Manning upright is the overarching goal because if the 37-year-old quarterback is lost, so is the season. This is the PFM window, and the Broncos have no chance to crawl through it without PFM.

Wearing a brace on the right ankle he re-injured last week in San Diego, Manning and offensive coordinator Adam Gase hobbled a fine line between risking Manning’s health on the one hand and playing it too close to the vest on the other. They ran the ball more than usual and Manning threw fewer touchdown passes than usual. But the Broncos won, 27-17, pulling them into a tie with the Chiefs for now.

“I worked hard all week to get ready to play physically, and certainly, our protection was excellent the entire game,” Manning told KOA afterward.

The Chiefs’ capable duo of edge pass rushers, Tamba Hali and Justin Houston, came into the game with 20 quarterback sacks between them and left with the same number.

“I thought Peyton did a good job getting the ball out fast, and I thought he worked the pocket pretty well,” said Chiefs coach Andy Reid. “There were times where we had pressure and you saw him slide and throw opposite (side), which isn’t an easy thing to do. He’s a pretty good quarterback. He did that and got away with a couple that most guys wouldn’t be able to get away with. But listen, we can do a better job there. We can get more pressure on him, and we’ll work on that.”

For the second consecutive week, the Broncos forced an AFC West opponent to settle for a field goal at a key moment, in this case after a first-and-goal at the Broncos’ 2-yard line. Meanwhile, the Broncos were doing what they’ve done all year — scoring touchdowns.

“I thought our red zone was outstanding,” Manning said after completing 24 of 40 passes for 323 yards and a touchdown. “This team (Kansas City) has been excellent in the red zone. They’ve held a lot of teams to field goals. That has been a big reason why they’ve been winning games. Teams have driven the ball, and they get down there and get three points (or) a turnover down there. The fact we were able to get three touchdowns down in the red zone and the two field goals by Matt (Prater), that was enough to win. That’s something we work on a lot. I thought that was critical. Two weeks in a row, our red zone has been critical.”

One intriguing aspect of the game was the Chiefs’ defensive game plan. In March, they announced they had signed Sean Smith, a big, physical cornerback, to join the accomplished Brandon Flowers in their defensive backfield. This was widely explained as a chess move to defend the Broncos’ Demaryius Thomas, a wide receiver too big and strong and fast to cover with a traditional, small defensive back.

So if it surprised no one else, it surprised me to look up early in the game and see the Chiefs allowing the Broncos to dictate the matchups in their defensive backfield. Rather than have Smith shadow Thomas wherever he went, they had Smith stick to his right cornerback position and cover whoever the Broncos split wide left.

Unsurprisingly, the Broncos sent Eric Decker over there early and deployed Thomas to the opposite side. With Flowers inside covering Wes Welker, rookie Marcus Cooper repeatedly found himself in man-to-man coverage against the most dangerous receiver on the field.

It didn’t take long for Manning to take advantage, hitting DT with a pass down the right sideline that flew almost 50 yards in the air and went for 70 before safety Quintin Demps finally pushed Thomas out of bounds. Two plays later, tight end Julius Thomas caught a short slant for a touchdown and the Broncos had a 10-0 lead.

This was exactly the scenario the low-scoring Chiefs could not abide. Playing catch-up is not their strength.

With the two teams scheduled to meet again in Kansas City in just two weeks, no one was going to disclose anything of even remote strategic significance. But you have to try, so I asked Manning if he expected Smith to shadow Thomas or stick to the right defensive side.

“They’ve done both,” he said. “Certainly, they’ve rotated different guys in the secondary. They’ve had some different guys playing than were playing earlier in the season. Every game you’re never quite sure how their rotation is going to be.”

Cooper, a seventh-round draft choice waived by the 49ers and picked up by the Chiefs just before the season began, has been surprisingly good considering how often he’s been targeted when the Chiefs play man-to-man defense in the secondary. Still, DT made both of his long catches against him and it will be interesting to see if the Chiefs change their strategy for the rematch in K.C.

Besides quarterback sacks, turnovers were the Chiefs’ other strength in building that 9-0 record. They got one early on a fumbled exchange between Manning and rookie running back Montee Ball deep in the Broncos’ territory. But the Denver defense got the ball back on the very next play when linebacker Danny Trevathan separated it from Chiefs fullback Anthony Sherman. So the turnovers canceled out. With neither sacks nor turnovers, the Chiefs couldn’t keep up.

They did manage an 80-yard touchdown drive spanning the end of the first and beginning of the second quarter, and then a 79-yard march on their next possession. That one-yard difference turned out to be pretty important. The Broncos’ much-maligned defense kept the visitors out of the end zone the second time, forcing them to kick a field goal.

“The defense came up big in spurts, and in the end it was enough,” interim head coach Jack Del Rio told KOA.

Turned out, the experts were pretty much on it. Even though the Chiefs came in with a better record, oddsmakers made the Broncos an 8-point favorite, mostly because the Chiefs hadn’t beaten anybody good. The Broncos had the league’s best offense, the Chiefs its best defense.

The Broncos’ 27 points were their lowest output of the season, although just barely, so the Chiefs defense did about as much as it could be expected to do. The offense, managed ably but soporifically by Alex Smith, did the same.

For all the excitement at the replica of the old barn off Federal Boulevard, this thing was little more than a foreword. The next two weekends will offer the Broncos their greatest challenge of the season — consecutive road games against New England and these same Chiefs.

“From a scheduling standpoint, I’m not sure I’ve ever done that before,” Manning told KOA. “There’ll be great familiarity between both teams. Unfortunately, we’ve got a really good team we’ve got to play in between.”

Finishing ahead of the Chiefs is necessary to win the division, a route that offers a slightly smoother road in the postseason, at least in theory. But if the Broncos were to lose these next two, the advantage bestowed by Sunday night’s win would likely disappear.

So this was a necessary but insufficient condition to get where the Broncos want to go.

“We knew when the schedule came out that these were going to be three critical games,” Manning said. “We hoped they were going to be critical. We hoped they were going to matter, because that meant we had taken care of business early in the season. So this was an excellent win. We’ll enjoy it tonight. We’ll be in there tomorrow studying this one and getting a head start on New England.”

As the players and coaches left the field Sunday night, Del Rio circled back to find Gase and congratulate him. Normally, when head coach John Fox is about, these two are peers, coordinating the offensive and defensive game plans. When you consider that they’ve managed these last two division victories in the absence of their head coach, you can understand the joy they felt at keeping the team rolling while Fox recovers from open heart surgery.

“Great, great night of football,” said an enthused Del Rio. “Two very good football teams going at each other. I thought our fans were tremendous. I was told on the way in we only had 74 no-shows, which means that place was full and rocking. It was awesome.”

Imagine how happy he’ll be if they’re still in first place the next time they get to play there.