Like the Arctic front sweeping across the country, the winds of change have whipped through the NFL this season and altered the landscape.
Nowhere is that more evident than the first day of the playoffs.
A year ago, Reid was still coach of the Eagles. Pagano missed most of last season battling cancer. Payton was serving a year-long suspension for his role in the "Bountygate" scandal. And Kelly was the widely coveted coach of the Oregon Ducks.
When the Chiefs play at the Colts, followed by the Saints at the Eagles, a fundamental reality of the NFL will be on display — situations change in a flash, and you had better win if you want to keep your job.
Reid flipped a U-turn with a Kansas City team that was 2-14 the previous season. Payton picked up where he left off with Drew Brees and the Saints' offense, and got a historically bad defense corrected. Pagano proved that he's a good head coach, and that the Colts wouldn't drop off a ledge with the departure of Bruce Arians, the interim who was named NFL coach of the year last season. And Kelly showed he could successfully install an NFL version of his innovative, up-tempo college offense.
"To some extent, this is what keeps getting everybody fired," said NBC analyst Cris Collinsworth, who will be in the broadcast booth for the Saints-Eagles game. "Every year we see really good coaches getting fired because these owners are seeing other coaches come into the league and turn 2-14 teams into playoff teams. It's happening all the time. That's what keeps the jobs turning for NFL head coaches."
Pagano, in his first go-round as a head coach, missed three months of the 2012 season after being diagnosed with a treatable form of leukemia. He returned in time to coach the Colts in a first-round game at Baltimore, which they lost.
"We sat in the locker room a year ago at this time disappointed after a loss to Baltimore," Pagano said this week. "We had a talk and I told those guys, 'Remember, remember this feeling because we're going to be right back here. Just remember the feeling that you have right now and let's make sure that once we get in position to do this again, that we don't have the same feeling coming off the field.'"
Then again, like all teams, the Colts have broken off their rearview mirrors. They seldom look back.
"It's hard to compare teams and seasons and all that stuff," kicker Adam Vinatieri said. "Because you've got different personnel, you've got a different set of circumstances. I think we can reflect on what happened last year, build on that, and I know we've done that. But moving forward, we have short memories."
The Saints have made the playoffs in four of the last five seasons, missing them only last season, when Payton wasn't around.
"Obviously, having him back here is great," quarterback Drew Brees said. "He has a way of just little things to just kind of remind you of the focus and the opportunity and why we are all here."
Also key to the revival of the Saints was the addition of defensive coordinator Rob Ryan, who took over a unit that last season surrendered an NFL-record 7,042 yards. The Saints were ranked fourth in total yards allowed this season with 4,891.
Kelly's Eagles turned their season around after a 3-5 start. They have won seven of eight, scoring at least 24 points in each of those final eight games.
"This is an interesting thing going on in Philadelphia," Collinsworth said. "If it lasts more than a year here, this thing does take on some legs. It's going to open up coaching candidates that probably the NFL wouldn't have considered in the past.
"While I don't think it's so drastically different — it's a lot of West Coast principles, a lot of spread-the-field principles that go on everywhere — it's definitely eye-opening to see some of the numbers that the Eagles put up."
It isn't just Kelly's fast-paced offense or innovative strategies that have the league intrigued, but his unconventional approach to nutrition, sleep, training and the like.
"Whether it's real or just the placebo effect, the players really believe the sports-science stuff, the alternate practice methods, the sleep regulation, the nutrition stuff," Collinsworth said. "They feel better than they ever have. It's at least opening a lot of eyes.
"It's not just the play-calling or the offense. It's, let's take this league and flip it upside down and look at it from the other way."