The unemployment ranks swelled even further later on Monday with the Chicago Bears' Lovie Smith, Kansas City Chiefs' Romeo Crennel, San Diego Chargers' Norv Turner and Arizona Cardinals' Ken Whisenhunt also getting the axe to bring the total to seven teams with head coaching vacancies.
The 5-11 Browns, who closed out the season on Sunday with a 24-10 loss to the Pittsburgh Steelers, were among the first to begin house cleaning by announcing Shurmur and general manager Tom Heckert had been relieved of their duties.
The news was quickly followed by the 6-10 Bills confirming they had sacked Gailey and the 4-12 Eagles announcing Reid was being relieved of his duties after 14 years in charge.
Reid's departure had been widely expected but still came as shock to many after a mostly successful tenure in Philadelphia leading the Eagles to six NFC East titles, five NFC championship games and a Super Bowl appearance in 2004.
His 140 victories are a franchise record and rank 22nd on the all-time NFL coaching list.
But a bitterly disappointing 2012 campaign that ended in a 42-7 loss to the New York Giants on Sunday signalled to owner Jeffrey Lurie that is was time for a change.
"Andy Reid won the most games of any head coach in Eagles' history and he is someone I respect greatly and will remain friends with for many years to come," said Lurie in a statement. "But, it is time for the Eagles to move in a new direction.
"Andy leaves us with a winning tradition that we can build upon and we are very excited about the future."
If there was a surprise it came in Chicago where Smith was sacked despite guiding his team to a respectable 10-6 record and narrowly missing out on a playoff berth.
In nine seasons in Chicago, Smith posted a record of 81-63 in leading the team to an NFC championship and Super Bowl appearance in 2006.
But in five of the past six seasons, the Bears have failed to make the playoffs and after a sparkling 7-1 start to the 2012 campaign stumbled down the stretch to again miss out on the post-season.
After a league worst 2-14 season, that earned the Chiefs the number one pick in 2013 draft, it came as no surprise that Kansas City would be looking for a new head coach.
It was a difficult season on and off the field for Crennel, who watched the losses pile up then looked on as linebacker Jovan Belcher shot himself dead at the team's training facility after killing his girlfriend.
San Diego fired both coach Turner and general manager A.J. Smith after the team went 7-9 and missed the playoffs for the third consecutive season.
Arizona also removed its coach and general manager with Rod Graves dismissed along with coach Whisenhunt.
The Cardinals started the season 4-0 but won only one other game as quarterback problems beleaguered the team.
Black Monday began with the Jacksonville Jaguars announcing they had fired general manager Gene Smith and was followed by the New York Jets dumping GM Mike Tannenbaum.
The Jets, however, ended the speculation swirling around Rex Ryan by confirming the under-fire head coach would be back next season.
"Rex Ryan will remain the head coach of our football team. I believe that he has the passion, the talent, and the drive to successfully lead our team," said Jets owner Woody Johnson on the team's website.
After a tumultuous 6-10 season, overshadowed by a quarterbacking controversy around the use of incumbent Mark Sanchez and polarizing Tim Tebow, Ryan was widely expected to pay for the Jets under-achieving results with his job.
With Ryan back for next season the speculation will now centre on the futures of Sanchez and Tebow in New York.
The Jets' sputtering offense ranked 30th among 32 teams, generating an average of just 299 yards per game.
Changes had been expected in Jacksonville after the toothless Jaguars finished the season tied with the Chiefs for the NFL's worst record (2-14).
"Now it is time for the Jacksonville Jaguars to begin a new chapter," new owner Shahid Khan said in a statement. "We're not looking back.
"I've made it clear from Day One that we pledge nothing less than to deliver the first Super Bowl championship to Jacksonville.
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