However, they did not invent the U-turn.
Although it isn't a common occurrence, several teams have made dramatic one-season turnarounds, sometimes coming out of nowhere to stun the pro football world.
Indianapolis did that last season with then-rookie quarterback Andrew Luck, going from 2-14 in 2011 to 11-5 and a playoff berth.
St. Louis went from 4-12 in 1998 to 13-3 the next year, the first full season of quarterback Kurt Warner. And Cincinnati followed a stinker of a 4-11 year in the strike-shortened 1987 season by rebounding to 12-4.
"Winning cures and camouflages all problems," said Boomer Esiason, quarterback of those Bengals teams. "From 1987 where people wanted to run me out of the city, until '88 when I was the MVP and people wanted to have a parade in my honor, I saw the mental anguish of losing and the mental euphoria of winning, all in a matter of a year. And the human nature that goes along with that."
Esiason has walked in those same cleat-steps the resurrected Chiefs are walking in now.
Go 1-0 and the world shrugs. Go 2-0 and it raises some eyebrows. At 3-0, players have a new bounce in their step and can't wait to get back to work.
"When we went from 4-11 to 3-0, then 4-0, then 5-0, then 6-0 and being on the cover of Sports Illustrated and becoming the story in the NFL," Esiason said, "everybody's having fun, all the players are going out to Thursday night meals, guys are going over to other guy's houses, guys are hanging out together — black and white, offense and defense, linemen and wide receivers, running backs and defensive backs. Everybody loves each other. Everybody loves each other because you're winning, and it's fun.
"You go to work and you put on the videotape and somebody makes a mistake in a game. The coach will point it out, and everybody will have fun at his expense and you'll all laugh.
"But when you're 2-14, the last thing you want to do is go to work. You're 2-7 and you're out of it — think if you're the Pittsburgh Steelers now, or the New York Giants, or Atlanta Falcons. Those teams are miserable, man. They don't want to go to work."
The Chiefs, who play at 8-1 Denver on Sunday night, have seen both ends of that spectrum in less than a year. They are the league's only undefeated team, and they didn't come out of nowhere. The additions of Coach Andy Reid and quarterback Alex Smith were huge, but this was a team that, despite winning two games, had six players selected to the Pro Bowl. It's almost more surprising that the 2012 Chiefs finished 2-14 than the current Chiefs being undefeated.
Last season's Kansas City team had the kind of potential-energy buildup that the 1999 Colts had heading into Manning's second season.
"About halfway through Peyton's rookie season, he really started showing he was going to be a great player," said former Colts coach Jim Mora, who like Manning was in his first season with the franchise. "That was part of it, but the other big thing was our defense got a lot better. That first year we were bringing guys in every week, having them for a couple weeks and letting them go. Bringing in new guys and letting them go. We were a bad defensive team."
That changed when Mora hired Vic Fangio as defensive coordinator. Suddenly, Manning, in his second season, was backed up by a solid defense that frequently gave the offense good field position.
It's a similar situation now in Kansas City. The Chiefs' defense has held opponents to 17 points or fewer in each game this season, joining the 1977 Atlanta Falcons as the only teams to do that since 1970. The Chiefs were 25th in points allowed last season, surrendering an average of 26.6.
"There are a lot of things that jump out at you," Manning said of the Chiefs' defense. "Statistically, they're No. 1 in all the major categories, but yeah, their ability to create points themselves as a defense, and certainly not giving up points — those are certainly two that jump out at you. There is quite a list of others that is impressive."
Good fortune has been on Kansas City's side too. The Chiefs have yet to beat a team that currently has a winning record, and the tough second half of their schedule includes two games against the Broncos, two against San Diego, and one against the Colts.
A favorable schedule sometimes factors into a quick turnaround but not always. For Warner's Rams in 1999, there were so many changes, it was hard to point to one as the key factor.