In terms of magnitude, the rally from a 24-point deficit against Seattle in 1979 has been matched, but remains unsurpassed.
It was made possible by one of the best decisions then-head coach Red Miller ever made.
Heading into this Week 4 game, the Broncos were embroiled in a quarterback controversy. Although Craig Morton is today remembered as one the Broncos' greatest legends, back in 1978 and 1979 he did not have the favor of many fans. Much of the public wanted Norris Weese, who replaced Morton late in Super Bowl XII. Weese had electric mobility but a so-so arm; Morton could barely move because of accumulated injuries, but still possessed a howitzer capable of beating any foe deep.
Weese was installed as the starter for the 1979 season. The Broncos opened with two wins in their first thee contests, but did so on the strength of their defense, which allowed just two touchdowns and 23 total points in the first three games (the Rams scored another seven on a fumble return in Week 2).
But in Week 4, the dam finally burst. Two turnovers and a 29-yard punt return allowed the Seahawks to start three drives from Denver territory; these accounted for 17 of the 34 points Seattle piled up by the time 5:32 had elapsed in the third quarter. The Seahawks intercepted Weese twice, dropping his season-long quarterback rating to 66.6.
Miller called for Morton, who initially resisted. He didn't make the mess; now he would have to try clean it up under circumstances that were adverse -- and that's putting it kindly, given that the daring, aggressive Seahawks were one of the most explosive teams of the day and seemed capable of putting up 48 or even 50 points on the beleaguered Broncos.
When Morton lurched onto the field, the past animus was forgotten; the fans roared. Then, as now, the backup quarterback is always a popular man.
But neither they nor the Seahawks knew what would come next: one of the most bracing doses of Mile High Magic ever administered.
Morton quickly completed four passes -- the last one of which was a touchdown strike to rookie offensive tackle Dave Studdard on a tackle-eligible play.
On the next play from scrimmage, Bob Swenson intercepted Jim Zorn. Three plays later, Morton found Haven Moses for an 11-yard touchdown, further narrowing the gap.
Dazed by the flurry of points, the Seahawks' potent offense crumbled under the weight of a revived Orange Crush. Seattle went three-and-out, and Herman Weaver shanked the subsequent punt, which sailed just 17 yards. On the next snap, Morton hit Upchurch for a a 35-yard strike.
In just two minutes and 34 seconds, Morton and the Broncos had scored three touchdowns -- a rapid-fire blizzard of points never seen before or since in team history.
"The old press box was shaking," recalled long-time team public-relations guru Jim Saccomano. "Gary Wright of the Seahawks, who worked 32 years for them, came and said, 'Are we in any danger?' I said, 'No, it's all fine.'
"But you could see them looking at each other and they knew this was not a good thing."
Again, the Seahawks went three-and-out, punctuated by a Tom Jackson sack that knocked Seattle back to its 5-yard line. Weaver blasted a 52-yard punt, but Upchurch sprinted 27 yards with the return to the Seattle 40-yard line.
Two Morton passes, one Otis Armstrong run and a Rob Lytle sweep later, the Broncos were at the Seattle 1-yard line, about to score. Armstrong fumbled on second-and-goal, but recovered it.
Watching from just 15 yards away at field level behind the end zone was the Broncos' director of public relations, Bob Peck.
In his 10th season with the Broncos, Peck had watched most games of the Broncos' rise to glory from his press-box perch. But on this gorgeous 81-degree day, Peck was in the end zone in a wheelchair, suffering from an inoperable, malignant brain tumor that would kill him within weeks.
From the corner of his eye, Lytle saw Peck. He swept right, then cut inside Paul Howard for the touchdown. He dove over the goal line, got up and ran to Peck, presenting him with the football.
"Now it would be a SportsCenter moment, and much else. None of that was the case," said Saccomano, who was hired by Peck to join the Broncos staff in 1978.
"Rob was asked about it, and he said it was just spontaneous. He saw him and gave him the football."
The Broncos held on for a win that would prove crucial. Denver ended up making the postseason at 10-6 by edging out four 9-7 teams -- including the Seahawks. If Morton doesn't rally the Broncos, the Seahawks likely don't have to wait until 1983 for their first postseason trip, and the Broncos don't further cement their place as one of the league's finest teams in the late 1970s.
But for Peck, his friends and family, the day would always mean something more.