Redskins quarterback John Beck prepares to throw a fourth-quarter pass. (John McDonnell/THE WASHINGTON POST)

John Beck leapfrogging Rex Grossman here Sunday for his first NFL start in four years, is obviously good theater. If Beck is serviceable to great and wins, Mike Shanahan’s decision is immediately vindicated. If he’s five-turnover dreadful and loses, it’s Rex vs. Beck all over again.

But imagine starting at quarterback the last five weeks of a season on a Super Bowl contender — only to be pulled in the third quarter of the last regular season game, which was tied a touchdown apiece.

And after getting the hook against the Vikings you never saw the field again that year, because Joe Gibbs was convinced Doug Williams would give the 1987 Redskins a better shot in the postseason of winning it all, which they did.

And your next stop was the Los Angeles Raiders, where an intense young Mike Shanahan also took turns starting, benching, lauding and loathing you — depending on what Sunday it was.

Is it any surprise then that Jay Schroeder, the only known passenger on the QB merry-go-rounds of Gibbs and Shanahan, still has this cruel karmic fate of dealing with two quarterbacks for one starting job more than two decades later?

“I’m doing it this year,” says Jay-bird, 50, and now the coach at Village Christian High in the Los Angeles suburb of Sun Valley. “One kid is a senior and the other a true freshman. My senior is more of a running threat, the freshman is a better passer, so I end up using them depending on the game situation.

“Changing quarterbacks during a season makes it tough on everybody, especially the team,” he adds over the telephone. “It’s tough on the two kids, that’s for sure.”

Asked if he ever told both his quarterbacks of his own precarious hold on the job in his career, which lasted nine years after Washington drafted him in 1984, Schroeder says, “Oh, they know what happened with me. They know very well.”

Jake Plummer, benched by Shanahan in Denver, was vocal a year ago after Donovan McNabb was controversially pulled for Grossman with two minutes left against the Lions. He painted My-Way Mike as a perfectionist, saying no matter how well he played, “it was never good enough for him.”

Schroeder wouldn’t go there with either Gibbs or Shanahan, who benched him in favor of Steve Beuerlein in 1988 and went back and forth between both quarterbacks before he was fired four games into Schroeder’s second year with the Raiders.

“But I can tell you it’s just hard on everyone,” he said. “It puts a lot of stress on the entire team. For either player, it’s tough just because you feel like you have to be perfect when you’re in there. It’s never a good thing going back and forth.”

That might be why many of Grossman’s main detractors want Beck to be given a fair shot at the starting job, not just a one-and-done opportunity in case he fails against Cam Newton and Carolina.

If Beck flourishes Sunday, he makes it much easier on his coach. If not, then Shanahan is faced with two scenarios the last 10 weeks of the season:

Does he let Beck develop and grow for at least a month — interceptions, losses and all — until he can fully evaluate him as an every-Sunday starter? Or does Mike The Coach have to be careful not to be at odds with Mike The Long-Term Architect and go right back to Grossman if Beck flounders out of the gate? Does he forget big picture while going back and forth between both guys, trying to siphon a playoff berth out of his menacing defense?

It’s not like it hasn’t been done to perfection before, circa ’87. Schroeder, benched twice that season by Gibbs for poor performances, including that game against Minnesota, still smarts from the signal from the sideline to come out in the third quarter, his last meaningful snap in a burgundy-and-gold uniform.

“I wish I would’ve got a shot,” Schroeder says now, believing he could have been Williams against Denver in the Super Bowl. “The game was tied, we were having a very good season.

“Of course you always think that when you’re taken out. The worst thought for any quarterback taken out and then put back in again and taken out again is, ‘What does he really want and how can I get it done better?’ It just puts more stress on the player. To be honest, you got to be extremely mentally tough to play quarterback in the NFL because so many other thoughts are going through your head about the game, the playbook, everything else that comes with it.”

Schroeder took some guff for his behavior at the end of the 1986 NFC championship game when he frantically waved Williams off after Gibbs told him to go in to replace a woozy Schroeder, who had been drilled by Lawrence Taylor at the end of a 17-0 loss.

“I look back at it, Doug and I were both competitors,” he says. “When I waved him off the field, it was the championship game and I had played every down of that game and I think every down of the season. I wanted to finish it.”

Of his first season with Shanahan, Jay-bird actually remembered the early faith his new coach showed in him. Down 24-0 in Denver in the fourth game that year and unfamiliar with a new system after the trade, Schroeder actually told Shanahan he could relieve him of the starting job if he thought it would help that game.

“He just said, ‘No, you need time to get this stuff down. We’ll be all right.’ We came back and won, 30-27 [in overtime].”

The hardest part for him, Beck, Grossman, heck, even his two quarterbacks at Valley Christian this year, Jay Schroeder said, was that gnawing feeling that never goes away when one guy isn’t head and shoulders better than the other guy:

“You always wonder, ‘How long is my leash?’ That feeling never goes away.”