It’s not too early to get really worried about the next time the NFL and the players union are due back at the bargaining table, as the end of the collective bargaining agreement after the 2020 season approaches.

It feels like a lot closer than three years away, actually. That's because the problems staring both sides in the face are staring them down right now, and they are serious. Shutting-down-the-sport serious. For both sides.

Problems like a couple of major advertisers … uh, well … pulling out. (It’s Viagra and Cialis. Sorry.)

Problems like upfront ad sales for the upcoming season, especially from traditional sponsors like auto and movie companies, being … uh, well … the softest in nearly a decade, since the big recession, according to a recent report. (That was the last time for this theme, promise.)

Problems like regular-season ratings dipping over much of last season, and the anxiety over whether that was just an exception or not.

And problems like players loudly objecting, for the second straight year, to how much less their stars (and others) are getting paid compared to those in the NBA.

There already were a stack of issues the union is ready to bring to the table that have gone on throughout the current labor deal: player discipline, concussions, the drug policy, Thursday night games.

But above and beyond those, these deals are about splitting the money. That’s what keeps bringing these sports to a screeching halt every several years; from 1998 to 2011, the NFL, NBA and NHL had a combined five lockouts. That’s the owners’ big stick, and clearly they haven’t been afraid to swing it.

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The NFL players haven't wielded their own big stick since the 1987 strike, the year of the scab games. The next time things got fractious enough for a season to be threatened, the owners flexed their muscles.

This time, both sides have ample reason to flex theirs.

The idea that the NFL bubble might be bursting after all these years — or is at least leaking — has to scare everybody in the sport, but, obviously, would scare the owners the most. The big bubble is television, and no matter how many other revenue streams the league uncovers in the next few years, TV is still the big cash cow, which means ad money … which means no one can ignore or shrug off the recent negative signs.

If that’s really a problem, they’re not going to give an inch to the players. History says they’ll try to take more, in fact.

And the players really sound as if they’re in no mood to take a step back. As much as major segments of the public smirk at them about their envy of their NBA counterparts, the players really are wondering why their careers are so fragile, their health put at the most risk, and their sport the most lucrative by light-years — but their salaries, guarantees and freedom are dwarfed by those in any other sport.

To get that in their favor will take more than a tweak to the system. It would take an overhaul, of everything, all the aspects of it the owners hold sacred.

And the players’ only leverage to get it is the same as the one the owners have. One side or the other would have to be ready to walk away and not play, and outlast the other.

Strike or lockout. Nuclear options all around.

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This isn’t to say either will happen in 2021. This is to say that, if the NFL isn’t at a crossroads right now, in the summer of 2017, it’s getting there fast. Owners aren’t getting what they want, suddenly and surprisingly. Players aren’t getting what they want, as they’ve pointed out more than once.

It’s not too early to worry about it — not for the league, the players or the fans who might not have the NFL to obsess over in a few years.