Duke students who serenaded Cooper Flagg with chants of “one more year” on Monday should prepare to be disappointed.

Even in the NIL era, the celebrated freshman would be sacrificing tens of millions of dollars if he returned to college for his sophomore year.

Flagg is the runaway favorite to be selected No. 1 overall in this year’s NBA Draft. Under the NBA rookie salary scale, he could earn as much as $13.8 million during his debut season in the league, Spotrac NBA salary-cap analyst Keith Smith told Yahoo Sports.

The rest of Flagg’s rookie deal, according to Smith, could pay him as much as $14.5 million in Year 2, $15.2 million in Year 3 and $19.2 million in Year 4. Then he’d be eligible for a potentially massive second contract worth up to three or four times as much per season.

If Flagg were to do the unthinkable and put off that NBA payday, he’d no doubt make a killing on the NIL market as a Duke sophomore. Between pay-to-play money and endorsement deals with established brands, those in the NIL space say Flagg could approach but not match the $13.8 million he could earn as an NBA rookie.

Austin Walton, the CEO and founder of Next Sports Agency, estimated to Yahoo Sports that Flagg could earn $6 million-$8 million in NIL money if he returned to Duke. That might be conservative, said Chris Brown, chief operating officer of Blueprint Sports, a company that seeks to match college athletes with potential NIL opportunities.

“Now he’d have bargaining power,” Brown told Yahoo Sports. “He’d know what that guaranteed contract would be worth as the No. 1 pick in the NBA Draft, and he’d be able to see how much Duke really needs him. His value would go way up.”

And yet even those in the NIL space argue that it would be fiscally unwise for Flagg to return to Duke next season. The injury risk is a factor. So is the threat of AJ Dybantsa, Darryn Peterson or another heralded prospect eclipsing him as the top draft choice. But the biggest issue is what Flagg could cost himself long term by pushing his NBA clock back by a year and delaying his potentially lucrative second contract.

Say that Flagg’s NBA team offers him a max contract after Year 4 of his rookie deal, a plausible outcome given his stature as a prospect. In 2029, he would be eligible to sign a five-year extension that would pay him a starting salary of 25% of his team’s salary cap. That extension would be worth $328.3 million over the course of the deal, Smith estimates, and would pay him about $56.6 million for the 2029-30 season.

That second contract balloons even more if Flagg distinguishes himself by being named All-NBA first, second or third team before the extension. In 2029, he would be eligible to sign a five-year extension that would pay him 30% of his team’s salary cap per year, meaning, by Smith’s estimate, Flagg would earn $393.9 million over the course of the deal and $67.9 million for the 2029-30 season.

If Flagg doesn’t enter the NBA Draft until after his sophomore year at Duke, that would mean he’d still be on his rookie deal through the end of 2029-30 season.

“That's one more year of delaying signing that second contract,” Smith said, “and that's where the big money is.”

As the No. 1 pick in the 2026 NBA Draft, Flagg would earn an estimated $21.1 million during the 2029-30 season, per Smith. That’s $46.8 million less than Flagg would earn that season under Smith’s best-case scenario if he’s already beginning his second contract. The gap is $35.5 million even if Flagg hasn’t yet distinguished himself as an All-NBA player.

A prospect of Flagg’s caliber staying in college for more than one year is virtually unprecedented in the one-and-done era. This is a guy who was hailed as the future No. 1 overall pick even before he held his own against the U.S. Olympic team as a 17-year-old or led Duke in every major statistical category as a freshman. Flagg returning to Duke would be bigger than Harrison Barnes returning to North Carolina to avoid the NBA’s looming work stoppage, bigger than Al Horford and Joakim Noah going back to Florida to chase back-to-back championships.

That far-fetched possibility had hardly been discussed until The Athletic published a profile on Flagg last month. Buried three-quarters of the way through that piece was Flagg saying that he has enjoyed his college experience and adding, “S***, I want to come back next year.”

That is not the same as Flagg saying that he intends to come back next year, but media outlets and social media posters ran with it just the same. Flagg only fueled the fire late in Monday’s blowout victory over Wake Forest when he responded to the “one more year” chants from the Cameron Crazies by smiling and making a “run it back” gesture.

When asked to clarify after the game, Flagg told reporters in Durham, “I don’t know what the future holds.”

“I’m living in the present right now,” Flagg said. “I’m living in the moment. Taking it day by day.”

Those comments might keep hope alive for Duke fans.

The math doesn’t.

Flagg would be costing himself tens of millions and risking injury or his stock falling if he returns to Duke. When the time comes, he’ll make the prudent decision.