Ten of the 32 head coaches that started last season, almost a third of them, lost their jobs to equal an NFL record, previously set in 2006, 1997 and 1978.
Their 10 replacements, one of whom has a Super Bowl win to his name as head coach, are currently fine-tuning new teams ahead of the 2022 season.
In an era where greatness is measured by longevity rather than playoff success, who are the elite coaches in the NFL right now?
Regular-season record: 290-143 (.720)
Six Super Bowl wins as HC
3 x Coach of the Year
Approaching 50 years in the league and with 27 of them spent as a head coach, no one can match Belichick's seniority or success.
The Patriots pulled a swift one on the New York Jets when they poached him in 2000 as Belichick has long since paid off the debt of a first-round draft pick. Simply put, he's the most successful head coach in the business and has been for well over a decade.
Tom Brady's brilliance certainly helped and his record as a general manager is certainly more up for debate than his coaching credentials.
But you won't find many of his ex-players ready to bad-mouth him, despite a dour demeanor that led to him being nicknamed 'Doom' as an up-and-coming defensive coordinator with the New York Giants.
Regular-season record: 233-135-1 (.633)
One Super Bowl win as HC
1 x Coach of the Year
Reid has followed on a similar path. He won a Super Bowl as an assistant before getting his big break in Philadelphia - taking the Eagles to the playoffs in nine out of 14 seasons and winning the NFC East six times.
But the Eagles lost four NFC Championship games and an epic battle for the Lombardi Trophy with Belichick's Patriots at the culmination of the 2005 season and his time in Philly came to an end.
The Chiefs immediately gave him another shot and he has over delivered on his mission statement - making the playoffs eight times, winning six division titles, two AFC Championships, and a Super Bowl.
His Chiefs have been in the AFC Championship Game in each of the past four postseasons.
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Regular-season record:154-85-2 (.643)
One Super Bowl wins as HC
Tomlin's star began to rise when he coached the Tampa Bay Buccaneers' defensive backs during a four-year cycle when the Bucs the NFL in total defense (fewest yards allowed per game), never ranking worse than sixth overall.
His influence was clear to see when the Buccaneers won the Lombardi Trophy in January 2003, recording a Super Bowl-record five interceptions, three of which were returned for touchdowns.
The Steelers snapped him up in 2007, since then he has delivered 10 playoff runs, seven AFC North titles, taken them to three AFC Championship Games and two Super Bowls. Rounding off his second season in Pittsburgh in style, he became the youngest head coach to win the Super Bowl at age 36.
Incredibly, he's never had a losing season during his 15-year run in Pittsburgh - a feat that Belichick couldn't manage in his first 15 years in New England or Reid in Philadelphia - although he is on course to emulate it in KC.
Regular-season record: 137-88 (.609)
One Super Bowl wins as HC
1 x Coach of the Year
Harbaugh comes from a family of football coaches and started on the career ladder as soon as he graduated in 1984. He landed his first HC position with the Ravens 24 years later, taking Baltimore to the AFC Championship game in his rookie year.
After another near miss in the AFC title game of 2011, Harbaugh took the Ravens to the Super Bowl in 2012.
Facing a San Francisco 49ers team coached by his younger brother Jim, Harbaugh's Ravens held on to win 34-31 in dramatic fashion as the coach instructed his punter to waste vital seconds before taking an intentional safety in order to deny the Niners one last chance.
Only four playoff appearances in nine years since that lone Super Bowl win are why he's not higher on the list, but he did lead Baltimore to a 14-2 regular season record in 2019.
Strangely overlooked for head coaching positions in the past few years, Bieniemy is regarded as the most successful coordinator currently working in the NFL and just gets onto this list ahead of Sean McVay and Pete Carroll.
The former NFL rusher guided RBs Adrian Peterson and Jamaal Charles, who made a combined seven pro bowls in eight seasons, as a position coach in Minnesota and Kansas City before stepping up to be the Chiefs' OC.
His offenses have ranked first in the league in two out of his four seasons in charge and never outside the top six.
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