The Monday after the N.F.L. regular season is a perilous day to be a head coach. This year, Brian Flores, Matt Nagy and Mike Zimmer all found themselves out of a job, joining Vic Fangio of the Broncos, who was dismissed a day before.

Jon Gruden of the Raiders and Urban Meyer of the Jaguars left their posts earlier in the season.

The round of firings this year encompasses several organizational tear-downs, as the Bears and the Vikings also shed their general managers, and the Giants began their assessments of Coach Joe Judge and General Manager Dave Gettleman.

Vic Fangio, Denver Broncos

The Denver Broncos fired Coach Vic Fangio after three losing seasons.

Fangio was dismissed a day after the Broncos lost to the Kansas City Chiefs, 28-24, and finished in last place in the A.F.C. West with a 7-10 record. The Broncos were in contention for a playoff spot heading into the last quarter of the season, thanks to one of the league’s top defenses, but then lost their last four games.

Denver has not made the postseason since their Super Bowl victory in the 2015 season. Fangio compiled a 19-30 record over three seasons.

The Broncos’ general manager, George Paton, who took over that job when John Elway moved to director of football operations in January 2021, will start looking for a new coach.

“George will have full authority to select the next head coach of the Broncos,” the team’s president and chief executive, Joe Ellis, said in a statement. “This is his decision and his program.”

There may also be turmoil in the owner’s box, too. The odds that the franchise will be sold this year rose after a judge in Arapahoe County, Colo., dismissed a lawsuit that contested the will of the former owner Pat Bowlen, who died in 2019.

Whoever takes over the team’s front office will inherit several top offensive weapons, including receiver Jerry Jeudy and tight end Noah Fant, and several top defenders, including safety Justin Simmons and linebacker Bradley Chubb. The team also has five picks in the first three rounds of the coming draft.

Brian Flores, Miami Dolphins

In a surprising move, the Dolphins dismissed Brian Flores on Monday despite a 9-8 season, and a seven-game winning streak that nearly vaulted Miami into the playoffs. In his three seasons as head coach, Flores held a 4-2 record against the division-rival New England Patriots and Bill Belichick, his mentor over his decade as an assistant there.

The Dolphins’ winning record in the 2021 season, like last year’s 10-6 finish, was not enough to get them in the playoffs, an absence that has stretched to five years.

“I determined the key dynamics of our football operation weren’t functioning at a level I want it to be and felt that this decision was in the best interest of the Miami Dolphins,” the team owner Stephen Ross said in a statement. “I believe we have a talented young roster in place and have the opportunity to be much better in 2022.”

Flores finished with a combined record of 24-25 after three seasons in his first head coach job. The team announced that it would retain General Manager Chris Grier.

Matt Nagy, Chicago Bears

The Bears dismissed Coach Matt Nagy and General Manager Ryan Pace on Monday.

Nagy had a spectacular debut in 2018, as the Bears finished 12-4 and made the playoffs for the first time in eight years, earning him the Coach of the Year Award. But two 8-8 seasons and a 6-11 season followed. His tenure ends with a 34-31 overall record.

Pace was at the club for seven seasons. He hired John Fox (14-34) and Nagy as head coaches and drafted quarterback Mitchell Trubisky (over Patrick Mahomes) in 2017.

Although Nagy had been the offensive coordinator at Kansas City, the Bears never developed a strong offense behind Trubisky. They turned to Andy Dalton and the rookie Justin Fields this season with mostly poor results.

Mike Zimmer, Minnesota Vikings

The Vikings fired Coach Mike Zimmer and General Manager Rick Spielman on Monday.

“It is time for new leadership to elevate our team so we can consistently contend for championships,” the team said in a statement. The Vikings have not made a Super Bowl since the 1976 season and have never won an N.F.L. title.

Zimmer was head coach for eight seasons, including three playoff appearances. The high-water mark was a 13-3 season in 2017 and a trip to the N.F.C. championship. But the team was 7-9 and 8-9 the past two seasons. Zimmer finishes his tenure with a record of 72-56-1.