The NBA is headed for a free agency "nuclear winter" in the summer of 2018 according to an NBA team executive, who spoke to ESPN's Tom MacMahon and Bobby Marks -- a market correction to the money that got tossed to free agents in the summer of 2016.

Free agents in the summer of 2016 enjoyed an unprecedented windfall, as several teams raced to spend the sudden influx of cap space afforded by the new TV deal. The cap spiked hard after the NBPA rejected an offer to smooth it over several years from owners, and as a result, many players -- like Timofey Mozgov and Allen Crabbe -- signed hefty deals. A general manager told ESPN teams were "guilty of a gold-rush mentality."

In 2017, everything swung back the other direction. Top-level stars still got paid -- Gordon Hayward signed a max offer to leave Utah, while the likes of John Wall, Stephen Curry, Kevin Durant, and James Harden all signed incredibly lucrative deals or extensions to stay where they were -- but a similar tier of mid-level players who enjoyed the windfall of 2016 suddenly found themselves in a tough situation. JaMychal Green and Nerlens Noel are two perfect examples -- very useful big men who were unable to land big offer sheets in restricted free agency. Green and Noel remain unsigned with everyone's money essentially tied up. Both are now more or less at the whims of their respective teams -- Memphis and Dallas -- and whatever contract those teams might offer.

The market correction was made even more harsh by the falling cap projections. Teams planned for the spike to continue to rise through the roof in 2017 and 2018, but instead, it leveled out. The 2017-18 cap is just over $99 million, which -- for teams who planned their futures very carefully for projections closer to $109 million in 2015 -- was a significant hit.

The Boston Celtics were hit hard by the falling projections. Where they previously had significant options for this offseason, suddenly the Celtics were forced to deal an important part of their core when they got a commitment from Gordon Hayward. The Celtics dealt Avery Bradley to the Detroit Pistons, acquiring Marcus Morris' team-friendly deal.

But Bradley's departure won't be the only effect the Celtics feel, and it might not be the most impactful either. Boston has two relatively difficult free-agent negotiations to work through next offseason in Isaiah Thomas and Marcus Smart, when players and agents might start to accept that 2016 was an outlier. Lucrative contracts will be difficult to come by, save for the most elite of the elite.

To make matters worse for the second tiers and lower, the elite tier in 2018 is loaded. LeBron James will likely hit the market, and he will probably be available for non-Cleveland contenders. Kevin Durant probably won't be likely to move, but he will technically be on the market again. Paul George and Russell Westbrook will both be unrestricted. Every one of those players -- and perhaps DeMarcus Cousins as well, for teams that can talk themselves past the issues -- will have suitors with fistfuls of money extended.

That might limit the market for Thomas, a star in his own right who plays at an incredibly deep position around the league and struggles perceptibly on the defensive end. Meanwhile, the market for a talented 29-year-old point guard looking for a "Brinks truck" might not be particularly competitive.

So where will that leave Thomas? It's not totally clear. The news on Wednesday that he won't need hip surgery is big, both for him and for the Celtics. His value is also higher in Boston than anywhere else -- he's a local hero and the beating heart of the team's offense. Boston can go into the tax to pay Thomas, but they won't be able to open up max cap space again to pursue a free agent (they'll have to settle for Al Horford and Hayward in consecutive offseasons -- a pretty phenomenal haul).

But while the Celtics certainly would like to keep Thomas happy, they won't negotiate a max deal when they are the only team driving up the market. Kyle Lowry's deal with the Toronto Raptors this offseason might be a good reference point (if not a perfect comparison): A three-year $100 million agreement that paid Lowry handsomely while limiting the long-term risk for Toronto. The only problem? A deal like that would likely send the Celtics skyrocketing into the tax, with current projections close to $50 million in tax money, assuming a few other factors that include a high Nets pick and a relatively fair deal for Smart. Boston's owners are far from stingy, but it's probably worth wondering whether the Celtics are close enough to contending to warrant that kind of money.

Teams don't often regret paying big money to good players. The Celtics probably won't be upset to hand Thomas an enormous check, but Thomas' timing isn't ideal -- the Celtics hold most of the leverage, and entering a "nuclear winter" of free agents, the negotiations might not be everything Thomas expects.