How much money is too much to pay an NFL quarterback?

Kirk Cousins is going to be expensive for Washington to keep longer than the 2017 season. After giving him the franchise tag for a second consecutive offseason, Cousins is set to make $23.94 million and become a free agent next spring.

Washington failed to negotiate a long-term deal with the quarterback before Monday at 4 p.m. ET. Now, Cousins will be locked into a one-year deal and unable to negotiate a new contract until the 2018 offseason.

Keeping Cousins beyond 2017 is a long shot for Washington. Franchise tagging him for the third time is unrealistic with the number jumping to more than $34 million, and a bidding war in free agency will likely be too hard for the quarterback to pass up.

So what’s it going to take for Washington to keep him? A whole lot of money. A record-breaking amount.

A month ago, the Oakland Raiders made Derek Carr the highest-paid player in football history with a five-year, $125 million contract that comes with $70 million guaranteed. In August, the Lions and Matthew Stafford agreed to a $135 million deal with $92 million guaranteed.

It will require more to keep Cousins, but how much is too much?

What should a franchise quarterback get paid?

The value of a franchise quarterback is mostly determined by whoever got paid last. Because Stafford got $27 million per year, the next gigantic deal for a quarterback will have to be a little more. And then it’ll be topped by the next contract after that.

Franchise quarterbacks never hit free agency, so there’s really no way for the market to get set any other way.

But if there was no baseline to build around and contract terms were built from scratch, what would a quarterback worth committing to for the long haul actually be worth?

Likely much more than what they’re getting paid now.

The difference between having a Tom Brady at quarterback vs. a Blake Bortles can be the difference between a team that wins a Super Bowl and one that can’t win more than a third of its games.

There’s no easy answer when trying to quantify how much of an offense’s production can be credited to the quarterback position. Maybe the best way to see the value of an elite passer is when a team loses one and has to rely on a backup to fill in.

A statistical study by the University of Missouri found that losing a quarterback for four games due to injury or suspension would drop a team’s win total by an average of 1.3 games. No other position affected a win total by even half that margin.

Not having a great player under center or losing one can crush a team’s chances at the playoffs. The Raiders dealt with 13 straight seasons outside the postseason — cycling through players like JaMarcus Russell, Kerry Collins, and Andrew Walter — before finally finding Carr.

With so much value at quarterback, what percentage of a team’s spending should go toward that position?

Fifteen percent? Twenty?

Few teams even go over 12 percent.

The salary cap is rising faster than contracts

For four consecutive seasons, the NFL’s salary cap has jumped by at least $10 million. It reached a new high again this March when it was set at $167 million.

But teams aren’t spending it as quickly. According to The Ringer, 13 teams had $5 million in cap space during the 2014 season while the other 19 were close to the spending limit. In 2016, 23 teams had at least $5 million in room.

Carr’s $25 million per year is a significant amount but represents less than 15 percent of the $167 million salary cap. It will also only count $15.6 million against the Oakland Raiders’ cap in 2017.

Four years ago, Eli Manning’s $20.85 million cap hit was close to 17 percent of the New York Giants’ $123 million salary cap.

The fear in giving a player like Cousins a blockbuster deal is that committing so much money to one player would inhibit Washington’s ability to build an adequate roster elsewhere. But the fast rise of the salary cap has made burdensome contracts a problem of the past.

Even if the team was on the hook for $26 million per year, that would be 15.6 percent of the salary cap in 2017 and would dip once the cap inevitably rises higher next year.

Just pay the man

Cousins is likely to play out the remainder of his contract, and that probably means he’ll become a free agent in 2018.

Giving him the record-breaking contract almost definitely required to keep him in Washington would be a risk. Letting him walk is also a risk.

There’s plenty of reason not to make Cousins the highest-paid player in the NFL. Yes, he made a Pro Bowl in 2016 with another extremely efficient season and some of the league’s best passing statistics. But he was atrocious in the red zone and completed fewer than a third of his passes inside the 10-yard line.

With all his passing production, Washington finished No. 3 in total offense but couldn’t crack the top 10 in scoring.

But the question shouldn’t be whether Washington wants to pay him like a top-five quarterback. The question is whether he’s worth 12-15 percent of the team’s salary cap — and the answer to that looks like a resounding yes.

Without him, Washington’s next best option looks like 2016 sixth-round pick Nate Sudfeld. If that doesn’t work out, the team has Colt McCoy or it can start digging for another player to be under center. That’s a position no franchise wants to be in.

Pay your quarterbacks, everybody. It’s worth it.