It has been one of the most enduring rivalries in sport. As the NFL has constantly evolved, two players have remained as the league's gold standard and on Sunday Tom Brady and Peyton Manning will do battle once again.
This weekend's duel between the New England Patriots and the Denver Broncos and two of the NFL's most celebrated quarterbacks is a high stakes one.
A place in Super Bowl 50 is on the line in a contest that marks the fourth time Brady and Manning have met in the AFC Championship game.
Overall this will be the 17th game in which Brady and Manning have faced off and, given the contrasting fortunes the duo have experienced this season, it is likely to be last.
While Brady, undoubtedly fuelled by a desire to send a message after the 'Deflategate' saga that - despite his eventually successful appeal against a four-game suspension - had a damaging impact on his reputation, has prospered with a Patriots offense hampered by injuries, Manning has floundered and relied heavily on the Broncos' stellar defense.
After going 12-4 despite key offensive player Julian Edelman missing multiple games and running back Dion Lewis seeing his season ended by a torn anterior cruciate ligament in November, the Patriots are in a great position to return to the Super Bowl having reclaimed the title with a dramatic 28-24 win over the Seattle Seahawks last year.
Brady was the mastermind as the Patriots made last Saturday's 27-20 divisional-round win over a Kansas City Chiefs team eyeing a 12th straight victory look startlingly routine.
By contrast, Manning's evidently average display in the Broncos' 23-16 defeat of an injury-ravaged Pittsburgh Steelers team in which Denver put the strain on the running game and the defense.
Manning's sharp decline has been tough and highly depressing to watch. Once considered the NFL's ultimate field general, the 39-year-old has hindered the Broncos' cause more than he has aided it this campaign.
Signs of a drop-off began to emerge in last year's divisional-round defeat to former team the Indianapolis Colts in which he played with a torn quadriceps muscle.
However, few could have predicted how poorly the five-time MVP would perform this year.
In his 18th season in the league, physical issues and an inability to put as much force behind his throws were to be expected, but his inaccuracy and the frankly dreadful decision-making Manning has displayed was not.
Manning threw just nine touchdowns to 17 interceptions in the regular season.
Not since his final season in Indianapolis in 2010 has he been picked off with such regularity and it will have come as a relief to many Broncos fans when Manning - after a four-interception game in a loss to the Chiefs - was forced to sit out in favour of Brock Osweiler because of a torn plantar fascia in his left foot.
Ultimately, despite the Broncos winning games with Osweiler under center, Denver coach Gary Kubiak decided he was not an upgrade on Manning, who was called on in the third quarter of their regular-season finale with the San Diego Chargers to help avoid a defeat that would have handed the AFC West title to Kansas City.
Yet, as Brady - despite being just over a year younger than Manning - shows no signs of slowing down, the 2015 season has long since had the feeling of a bizarre and predominantly disappointing swansong for Manning.
The only question that remains is how his glittering career ends. His apparent personal desire to keep playing aside, most would expect the Broncos to cut ties with Manning and move on if Sunday's game ends in a home defeat.
Victory over his greatest foe and then on the biggest stage of them all at Levi's Stadium in Santa Clara two weeks on Sunday would allow Manning to ride off into the sunset on top.
With Brady attempting to win a fifth Super Bowl title at a venue just 25 miles outside of his home town, the overwhelming expectation is for the Patriots to put the Broncos to the sword.
But Manning, for all his faults, will forever carry a perennial mystique. Nobody would be surprised if his career ends with one final flourish.