Reason No. 1 the exhibition season, which ends tonight, is meaningless?
Well, the two best quarterbacks in the game today sat out the entire exhibition season. Sure, Tom Brady and Peyton Manning both had injury issues. Manning even underwent minor knee surgery recently.
But both are NFL ironmen. Manning has never missed a start, ever. Brady has never missed a start since taking over the No. 1 job in New England back in Week 3 of the 2001 season. So there's little doubt that both would have found a way on the field if the games actually mattered.
(For the record, the NFL doesn't want media to use the term "exhibition" to describe what it calls "preseason" football. However, because the best players don't play, and because they are in fact exhibition games that count for nothing in any way, we'll continue to accurately describe them as "exhibition" games.)
Of course, there's consternation today as both Indy and New England went through the entire exhibition schedule without generating a single TD from their starting offenses. The Colts fumbled and bumbled through a 1-4 exhibition season. The Patriots, 19-0 in their last 19 regular season games, were 0-4 in the exhibition season.
However, "starting offense" is a misnomer, considering the exhibition offenses were led by Jim Sorgi and Matt Cassell who, we can say in no uncertain terms, are NOT destined for Canton.
The ironman status of both Brady and Manning, meanwhile, is just one of the many reasons why they represent not just a great rivalry today, but the greatest quarterbacking rivalry in history.
Both are champions. Both have won MVP awards in Super Bowls and in the regular season. Both are among the most statistically dominant passers in history. And both have already engaged in some of the great battles of the 21st century.
Hell, just look at their last two meetings. In the 2006 AFC championship game, Manning pulled off the greatest second-half comeback in conference-title game history, earning his first Super Bowl appearance. It was a thrilling game by any measure.
Brady responded last year during the regular season, leading two fourth-quarter TD drives to overcome a 20-10 deficit on the road and pull out a 24-20 win for the Patriots that preserved their march to an undefeated regular season. The Patriots entered the game 8-0. The Colts were 7-0. It was the latest meeting ever of undefeated teams in NFL history.
So we witnessed history in each of their last two meetings alone. And each time they play, it's the most watched game of the year.
The best part? The two future Hall of Famers square off for an 11th time on Nov. 2, in a Sunday night primetime battle. A 12th battle may be on the horizon in January, no matter how poorly their respective teams performed in the exhibition season. 
It all adds up to what we declared last year was the greatest quarterbacking rivalry ever.
But, as we also noted last year, the Cold, Hard Football Facts do not take proclamations of "greatest ever" lightly. We handed down this verdict of the Brady-Manning rivalry only after a thorough study of the greatest QB battles of the pigskin past.
Here are those great rivalries, and why they fail to live up to Brady vs. Manning.
Sammy Baugh vs. Sid Luckman (1940s)
These guys basically invented modern quarterbacking, turning it into a position we'd recognize today: the guy who takes almost every snap and is generally the sole player responsible for passing the ball. They played three times for the NFL championship (1940, 1942, 1943), and were as great as any quarterbacks who have ever played the game, putting up numbers that have stood the test of time. Baugh, the quarterback on the Cold, Hard Football Facts All-Time 11, completed 70.3 percent of his passes in 1945, which remains the second highest completion percentage ever; Luckman, believe it or not, remains Chicago's all-time leading passer, nearly 60 years after he last suited up for a game.
Why it fails to live up to Brady-Manning:
As good as they were, nobody saw Baugh and Luckman play except the folks in attendance on gameday; they  dominated the NFL in the talent-depleted World War II Era, when many of the game's greats were off fighting more important battles.
Otto Graham vs. Norm Van Brocklin/Bob Waterfield (1950s)
Graham led the greatest dynasty in football history, the 1950s Browns; Van Brocklin and Waterfield were the two-headed Hall of Fame monster who quarterbacked the greatest offensive juggernaut in NFL history, the 1950s Rams. These guys met in the NFL championship game three times in six years (1950, 1951 and 1955) and essentially were the sexiest quarterbacking stars during the decade in which the NFL began to come of age; L.A. hotshot Waterfield, for example, gave the rivalry the social-pages sizzle Brady does today: he married buxom Hollywood hottie Jane Russell, she of some of the most amazing breasts in pre-plastic surgery Tinseltown history.
Why it fails to live up to Brady-Manning:
Van Brocklin and Waterfield had their own little rivalry going on within the Rams organization, as the two Hall of Famers vied to lead the most explosive offense in history; the third wheel, as it always does, tends to ruin a relationship and makes for confusing pre-game hype headlines.
Bart Starr vs. Johnny Unitas (1960s)
Starr and Unitas won eight championships between them in the 13 seasons from 1958 to 1970. They were the NFL's two most recognizable names of the 1960s, the era in which pro football became the undisputed king of North American sports, they both put up historic numbers, and were winners in what are probably the two most famous games in NFL history (Unitas in the 1958 championship game, Starr in the Ice Bowl). If not for Brady vs. Manning, this would probably be No. 1.
Why it fails to live up to Brady-Manning:
Playing mostly in an era when their were no playoffs, only a single NFL championship game, Starr and Unitas never met in the postseason. They had a chance, once, in 1965, when the Packers and Colts faced off in a rare tie-breaker playoff to determine the West's representative in the NFL title game. But Unitas was injured, so Baltimore's  quarterbacking duties fell to running back Tom Matte and football fans were robbed off a chance to see two of the game's greatest quarterbacks square off for the one and only time in a do-or-die battle. 
Terry Bradshaw vs. Oakland's Ken Stabler (1970s)
Bradshaw and Stabler were the two most high-profile players on two of the most high-profile teams of the 1970s; both were Super Bowl winners and from 1972 to 1979, at least one of these quarterbacks led their team to the AFC championship game. The two squared off to in the AFC title game three straight years from 1974 to 1976, with the winner going on to capture the Lombardi Trophy each time. The Steelers and Raiders also played a number of memorable regular-season games from 1973-79 that had an impact on the playoff picture.
Why it fails to live up to Brady-Manning:
Stabler crafted one of the great seasons in NFL history in his championship year of 1976, but put up some rough numbers in many other years and today finds himself on the outside looking in at the Hall of Fame. Even adjusted for their Dead Ball Era rivalry – in which it was incredibly difficult to pass – the lifetime numbers of Bradshaw-Stabler pale in comparison to Brady-Manning. Bradshaw is one of the best big-game quarterbacks of all time, but even for his era, his regular-season production was hardly great and, at times, downright awful.
Bradshaw vs. Roger Staubach (1970s)
The uber-talented glamour quarterbacks of the NFL's marquee franchises of the 1970s combined for six Super Bowl championships and three Super Bowl MVP awards over the course of the decade. They also met twice in two of the most exciting Super Bowls of all time. Bradshaw was one of the best big-game quarterbacks in history. Staubach retired with the highest passer rating in history (83.4, since surpassed by many players from the pass-happy years that followed).
Why it fails to live up to Brady-Manning:
The rivalry was elevated mostly by the hype of the two Super Bowl games against each other. Playing in different conferences, they rarely squared off in the regular season. And both were surrounded by tons of Hall of Fame talent, which means they didn't quite lord over the image of their teams the way Brady and Manning do today.
Dan Marino vs. Joe Montana (1980s)
Marino vs. Montana was the great quarterbacking debate of the 1980s. The two are Hall of Famers, put up amazing numbers and their names alone reek of quarterbacking awesomeness.
Why it fails to live up to Brady-Manning:
Marino vs. Montana was more a rivalry in the sports pages than it was on the football field. Playing in different conferences, the two squared off just four times in the regular season. And their lone postseason meeting in Super Bowl XIX turned out to be no contest at all. Montana's 15-1 49ers destroyed Marino's 14-2 Dolphins, 38-16, in what was supposed to be one of the great power match-ups in history. They were awesome, but they never produced the annual head-to-head fireworks of Colts-Patriots.
Steve Young vs. Troy Aikman (1990s)
Young & Aikman were the last two Super Bowl MVP quarterbacks to face off in the regular-season before Brady-Manning played each other last season. They met in the NFC title game three straight years from 1992 to 1994, with the winner capturing the Lombardi Trophy each time. Young's 49ers and Aikman's Cowboys also played a series of memorable regular-season games, too.
Why it fails to live up to Brady-Manning:
Young and Aikman won every NFL championship from 1992 to 1995 and then – poof! – the rivalry was essentially over. Neither won another NFL title and their teams fell from their lofty heights soon after.
The Brady-Manning rivalry, meanwhile, is now in its eighth season and – despite the exhibition absences – the hype shows no signs of ending anytime soon. In fact, it's only getting bigger. Tune in Nov. 2.