Gang Green Nation discusses what could (and likely would) have happened had Peyton Manning forgone his senior year at Tennessee (he finished school in three years and used his senior year to focus solely on football) and entered the NFL Draft in 1997, the year the Jets had the #1 overall pick. GGN cites an article in the NY Post which discusses how Peyton would likely have been drafted by the Jets, parring him with then-Jets coach and football president Bill Parcells. Parcells' staff in New York at the time consisted of assistants named Charlie Weis, Romeo Crennel, and some dude named Bill Belichick.
As you may recall, following the 1999 season, Bill Parcells turned the Jets head coaching duties over to Belichick. Belichick was on the job for, roughly, two days before bolting with Crennel and Weis to the Patriots. John B asks the question, "What if?"
Would Bill Belichick have left for New England knowing he was leaving behind a young franchise quarterback and would have to face him twice each year? Maybe he doesn't. That would have given the Jets a Hall of Fame coach and deprived the Pats of one who built a dynasty.
The article BBN links to offers some interesting scenarios for time travelers looking to go back into the past and completely screw-up NFL history. Prior to Bill Belichick taking over the Patriots and Peyton Manning getting drafted by the Colts, both franchises were considered inferior to teams like the 49ers, Cowboys, Broncos, and even the Jaguars. Now, both are considered the best the NFL currently offers, creating a modern rivalry between the teams that echoes Celtics v. Lakers, Yankees v. Red Sox, and Leno v. Conan.
Imagine how different the NFL would be today with a NY Jets team coached by Bill Belichick and quarterbacked by Peyton Manning.