The NFL calendar has reached a slow point for all but two teams, and so conversations within league circles tend to meander. Earlier this week, an agent and a team salary cap manager drifted into hypothetical territory. How much, they wondered, would top quarterbacks make in free agency without a salary cap?

“My God,” the agent said later. “Some of these owners would go crazy and pay these quarterbacks $40 million to $45 million. They’d spend so much money they wouldn’t put enough players around them to win. Or they’d spend so much money they’d possibly lose money.”

The question is perhaps most compelling in the case of Tom Brady, who on Feb. 5 will attempt to lead the New England Patriots to their fifth Super Bowl title under his direction. Brady is, at once, one of the greatest athletes and biggest bargains of his generation. His career earnings have been stifled through the salary cap system and through his own choice.

Brady volunteers to leave money on the table every season by way of his annual salary, even considering the artificial cap brokered by the NFL and the NFL Players Association. Everybody knows he is underpaid. But how much has Brady’s salary been discounted in real-life dollars? What would he make without a salary cap?

Brady has been, in the words of former Green Bay Packers vice president Andrew Brandt, “historically and perpetually and perennially incredibly undervalued within the system.” And Brady has asked for that status, deciding repeatedly to sign contracts and restructure them to give the Patriots flexibility to sign other players.

Brady is uniquely situated, too, to accept less than his market value: He makes plenty in endorsements, and his wife, supermodel Gisele Bundchen, earned $30.5 million last year, according to Forbes’s estimate.

“Clearly, you can say New England has a systemic advantage, where they’ve had an A quarterback who’s playing for B pricing,” one high-ranking AFC executive said.

Brady signed a two-year, $41 million contract extension before this season that restructured an existing deal. The contract, which included significant bonuses, counted $13.7 million against the salary cap this year and will pay him $14 million next season. Given the demand for and importance of quarterbacks, it might represent the best value in professional sports (and almost certainly would if not for the NBA’s maximum salaries, which artificially limit the earning power of stars such as LeBron James).

New England Patriots quarterback Tom Brady celebrates a touchdown by running back Dion Lewis during the divisional playoff game against the Houston Texans. His 2017 salary is slated to pay him $5 million less than Houston’s Brock Osweiler, who signed a $72 million deal last offseason, and $6.3 million less than Miami’s Ryan Tannehill. AP photo

In a cap-free NFL, Brady’s annual salary wouldn’t need to be constrained to so small a figure to accommodate the rest of a 53-player roster and could rocket upward, particularly when his value is compared to those of his peers.

Brady’s salaries are comical in comparison to other, lesser quarterbacks. His 2017 salary is slated to pay him $5 million less than Houston’s Brock Osweiler, who signed a $72 million deal last offseason, and $6.3 million less than Miami’s Ryan Tannehill. Andrew Luck will earn an average of $24.6 million over his partially guaranteed five-year deal, signed last offseason.

So what is Brady actually worth? From a statistical sense, football’s interdependence between players poses a challenge. Baseball and basketball provide enough individual plays to create streamlined measurements of a player’s value, such as wins above replacement or win shares. In football, every player is constantly connected to the performance of his teammates.

“That’s a tough one,” said David Berri, an economics professor at Southern Utah University. “In those other sports, you can separate the player from the teammates. I can tell you what Mike Trout is worth. I can tell you what LeBron James is worth. The problem with Tom Brady is he doesn’t do anything by himself.”

Berri used European soccer as a model for his best estimate. Before it changed its player acquisition rules in recent years, it employed essentially an open market. In the unrestrained system, Berri said, economic studies found that, on average, teams spent 70 percent of their revenue on player salaries. Berri said he would expect market forces to affect the NFL in similar ways with no salary cap.

The going rate for top-tier quarterbacks approached $25 million per season last offseason under a system in which roughly 48.5 percent of revenue goes to players. If NFL teams behaved like their European soccer counterparts in a free market, then the top quarterbacks – like Brady – would make about $36.1 million.

The removal of a salary cap would not mean unlimited spending. Owners still would have to manage revenue and payroll to turn a profit. In the uncapped Major League Baseball, “everyone has a salary cap,” said Brandt, who now writes a column for Sports Illustrated’s MMQB. “They just call it a budget.”

If the NFL did away with its salary cap and Brady became a free agent, it would not mean that all 32 teams would bid on Brady. Only the teams with the biggest payrolls and quarterback needs, Brandt said, would be likely to spend on him. So while the salary cap would no longer stifle his earning potential, his options would dwindle.

“He’d have a limited marketplace,” Brandt said.

Still, it would take only two large-market teams to bid up Brady’s salary far beyond his current value. A very select number of players, almost all quarterbacks, have proved they can sustain success regardless of their supporting cast.

“Truly franchise-defining players that change the game – there are less of those in football than baseball or basketball because of the nature of the sports,” Brandt said.

Brandt hazarded an estimate of double what the highest-paid quarterbacks currently make, which would put Brady’s annual salary somewhere approaching $50 million. While he said he could see it landing closer to $35 million, the competitive nature of some owners could override sensible business judgment.

“Imagine walking into Jerry Jones’s office, and you try and tell Jerry Jones we don’t have enough money to do something,” the anonymous agent said, laughing. “It’s different when the NFL gives you a prepaid credit card every year called the salary cap.”

On the field in two Sundays, when he looks over the Atlanta Falcons’ defense, Brady’s salary will become wholly irrelevant. But as the Patriots built their latest Super Bowl roster, they used Brady’s willingness to be paid at a discount and the NFL’s system to their advantage. The Patriots, as they always seem to do, already have come out ahead.