After all they have done to protect their marquee golden boys from angry predators, the NFL could not possibly have expected this kind of quarterback upheaval.

Mason Rudolph in for Ben Roethlisberger (elbow) for the rest of the Steelers season. Both Teddy Bridgewater and Taysom Hill in for Drew Brees (thumb) for the next six weeks, at least, for the Saints. Kyle Allen in for Cam Newton (foot) on Sunday for the Panthers. Luke Falk in for Trevor Siemian, who was in for Sam Darnold, on Sunday for the Jets. Gardner “Mustache” Minshew in for Nick Foles (collarbone) this past Thursday night for the Jaguars.

Then there is Daniel Jones (the future) in for Eli Manning forever for the Giants. Dwayne Haskins (the future) waiting to replace Case Keenum with the Redskins. Tennessee’s Ryan Tannehill waiting to replace Marcus Mariota (performance). Josh Rosen (tanks for nothing) in for Ryan Fitzpatrick for no-one-knows-how-long in Miami.

ESPN Stats & Info reports that Allen is the 40th different starting QB used by teams this season, the most through three weeks of a season in the Super Bowl era.

Hall of Famer Gil Brandt tweeted, “Officially this will be the first time in NFL history that 20 quarterbacks 26 years old or younger will start in the same week.”

The revolving door has been dizzying, and this game of musical quarterbacks has been unsettling for franchise power brokers and fantasy football owners alike.

Once upon a time, Bill Belichick had a backup named Tom Brady when Mo Lewis knocked Drew Bledsoe out into the Charles River the night of Sept. 23, 2001. Brady is somehow still quarterbacking the Patriots on Sunday, six Super Bowl championships later.

No one today has a Tom Brady riding in from the bench to save a season.

So coaches and GMs are forced to find a way to somehow keep hope alive and convince their fan base — and players — that expectations do not change, there are no excuses, Next Man Up and all that.

The Steelers are too proud an organization to roll over, but their fortunes are suddenly in the hands of Rudolph, a Big Ben clone drafted in the third round out of Oklahoma State in 2018.

He won’t be throwing to Antonio Brown, but he does have his favorite college receiver at Oklahoma State, James Washington, across from JuJu Smith-Schuster.

“I don’t think anything’s changed because everybody has faith in Mason right now,” Washington told The Post by phone. “You gotta give him at least a chance. I think everybody’s riding with him, and so are we.”

Washington — 16 catches, 217 yards and one touchdown as a rookie and 4-for-74 this season — was the 60th pick; Rudolph was the 76th pick.

“It feels like college is starting all over again,” Washington said.

Washington was 226-4,472-39 TDs at Stillwater. Rudolph threw 13,618 yards with 92 TD passes. Ah, memories.

“We were actually playing [the University of] Pittsburgh, and it was the first play of the game, we were like on the [9-yard] line,” Washington recalled. “I had an out route, and he gave me a post, and I’m like, ‘A post on the [9-yard] line, you’re backed up in the end zone, I don’t know.’ They were in Cover 4, so I could see what he was saying.”

Touchdown.

“He bombed it,” Washington said. “It’s on YouTube.”

Then there was a game against Virginia Tech.

“We were talking before the game, I needed a certain amount of yards to become Oklahoma State’s leading receiver,” Washington said. “He had already became Oklahoma State’s leading passer, and he told me before the game, ‘I’m gonna help you get that, we’re gonna be all right.’ It was like beginning of the third or fourth quarter, and it was kind of the same deal, he gave me a post and I was in the slot that time. It was me one-on-one with … that nickel there, and he puts it out there again and with that post [route] made me Oklahoma State’s leading receiver.”

Five quarterbacks — Baker Mayfield, Darnold, Josh Allen, Rosen, Lamar Jackson — were drafted before Rudolph, who was 12-for-18 for 112 yards, two touchdowns and one interception last week in relief of Roethlisberger.

“He throws a tight spiral, and he puts some heat on it,” Washington said. “He’s got that strong arm that he just shows off, it seems, like every play. There’s times when you feel like, ‘I don’t think he can sneak it in there,’ he’ll sneak it between two linebackers closing, and it’s crazy.”

Washington believes the Steelers believe in Rudolph.

“He’s got the starting offensive line in his ear every single day, telling him, ‘No matter what, if it’s you or [Roethlisberger] back there, we’re gonna protect you,’ and us as receivers, we gotta make plays for him and keep his confidence high. I think this offense’ll be pretty good,” he said.

Bridgewater has thrown one TD pass since returning from a devastating knee injury in Minnesota before the 2016 season.

“It’s a good time for Teddy to be able to step up and be that presence in the huddle,” Saints running back Alvin Kamara said.

The uber-athletic Hill, who has played tight end and is a core special-teamer, has thrown seven passes as a gadget quarterback and rushed for 204 yards and two TDs.

“He’s got a live arm, quick release,” Saints coach Sean Payton said.

Allen, with his 31 career passes, was an undrafted free agent in 2018.

“We believe in him,” Panthers running back Christian McCaffrey said.

Jones, the sixth pick of the 2019 draft and new Giants franchise quarterback, and Falk, a sixth-round pick of the Titans in 2018 who threw for 14,481 yards and 119 TDs at Washington State, will be making their first NFL starts on Sunday.

Rosen replaces Ryan Fitzpatrick in Miami, and we should say a prayer for him.

The Eagles were fortunate when Foles became the savior who stepped in for Carson Wentz and won Super Bowl LII. The Rams were fortunate when Kurt Warner replaced Trent Green and led the Rams to the Super Bowl XXXIV championship.

The 1999 Jets were not as fortunate.

A warm, sun-splashed day that began with Super Bowl dreams ended in the shocking death of a season when Vinny Testaverde ruptured his Achilles tendon attempting to recover a Curtis Martin fumble. A devastated Bill Parcells would turn to Rick Mirer.

“I think our hopes were up so high that year that it seemed to take a lot of the air out of our sails,” Martin said. “It took us some time to regain that confidence.”

By the time Ray Lucas relieved Mirer and injected the Jets with confidence, it was too late for the playoffs.

“I think in these situations, your tendency is to allow your ability to shift to the mood of the team,”

Martin said, “and when the mood goes down, the playing goes down.”

Such is the battle that every team and every city that lost its starting quarterback or is turning its lonely new eyes to a replacement will be fighting.