So now that NFL clubs unanimously voted to shorten the current collective bargaining agreement it seems clear what's next for the league and its players.

Trouble.

The players won't be giving back any of their gains, Gene Upshaw says. (Getty Images)

The NFL hasn't had a work stoppage since the 1987 strike, when the league called on replacement teams to replace off-the-job veterans. But after what happened Tuesday morning, it sure looks as if that streak might be in danger.

"If they want out of the deal," a defiant Gene Upshaw, executive director of the players union, warned back in February, "there's nothing we can do about it. But we'll be prepared."

Translation: The players could walk or exercise decertification tactics it used to get free agency after the 1987 strike.

That, of course, is what's known as a threat, and the NFL responded Tuesday by, basically, calling Upshaw and his union on it. If the decision wasn't a surprise, the unanimity of the response should have been. If nothing else, NFL owners signaled they're together on this subject.

And that's why I think we're looking at trouble. It could be a lockout. It could be a strike. But it's definitely a threat.

Remember, the last time the collective bargaining agreement was imperiled was 2006, when small-revenue and large-revenue owners were divided in their approach to the future. Then-commissioner Paul Tagliabue pulled them together at the last minute and pushed through an extension.

This time, though, owners are not divided. They're unanimous in their opinion that what they have now is not working, while Upshaw is just as certain that what they have now is. Somewhere in between there's a dialogue waiting to happen.

"Everyone's doing well," Upshaw said in February. "The owners say they're not making money. I think everyone is making money. This isn't hockey where the players agreed to a 25 percent pay cut. We're not going to do anything like that."

Maybe, but there must be changes in the current deal, otherwise you could be looking at future Sundays in September without the NFL.

Look, the NFL's position is clear: It doesn't concede that clubs aren't making money; what it basically says is that clubs aren't making enough money. In a statement issued by the league Tuesday morning it acknowledged "the NFL earns very substantial revenues" but complained that more than half that money -- $4.5 billion this year -- goes to player costs.

"In addition," the statement said, "as we have explained to the union, the clubs must spend significant and growing amounts on stadium construction, operations and improvements to respond to the interests and demands of our fans.

"The current labor agreement does not adequately recognize the costs of generating the revenues of which the players receive the largest share; nor does the agreement recognize that those costs have increased substantially -- and at an ever increasing rate -- in recent years during a difficult economic climate in our country.

"As a result, under the terms of the current agreement, the clubs' incentive to invest in the game is threatened."

Two issues, in particular, seem to rankle league owners: 1) The inability of clubs to recoup bonuses to players who breach their contracts or refuse to perform, and 2) a pay scale that rewards unproven rookies with rich contracts substantially higher than those of most veterans.

"Our objective," said the league owners, "is to fix these problems in a new CBA, one that will provide adequate incentives to grow the game, ensure the unparalleled competitive balance that has sustained our fans' interests and afford the players fair and increasing compensation and benefits."

And if that doesn't happen? There's always the fall foliage in New England.

While owners pledge to "do our best to achieve a fair agreement," there's the question of what exactly is fair? Upshaw has made it clear he thinks that what the league has now hits just the right note, which is great except his partner just told us it disagrees so vehemently it wants out of the deal.

So now what?

As I said, nothing will happen immediately. There will be plenty of rhetoric from both sides -- probably a few threats, too -- but the game as you know it will not change this season or next.

Unfortunately, neither will the two positions.

"It means that, as they say during the draft, we're on the clock," Upshaw said Tuesday morning on Sirius NFL Radio. "That's basically what it means."

For the moment, the clock is everyone's friend. If there's one lesson we learned from the last experience it's that nothing gets done until it absolutely, positively must. In 2006 the NFL and the players association kept extending deadlines to resume collective-bargaining negotiations until they found common ground.

And that could happen again. But so could something else, and that's a rockier road to the finish. Because today's action signaled that this time league owners are unified, and that will make a compromise more difficult to achieve.