For the National Football League and its fans, there has never been a weekend more worthy of celebration.

The 2010 NFL season is likely to be remembered as the zenith for a North American sports league, the climax of 50 years of work in which all five television networks that feature NFL games have shattered records for viewership.

But the spectacle of this weekend's four divisional playoff games also comes with a pinch of anxiety. The reality is that the league's runaway success isn't likely to be repeated, ever, especially if management and labor can't reach a new collective bargaining agreement and the owners lock out the players and cancel games next season.

The NFL acknowledges that its recent prosperity hasn't tackled its nagging concerns. "All is not perfect in the Land of Oz," said NFL spokesman Greg Aiello.

There were many reasons for the NFL's surge this season. Events such as Michael Vick's re-emergence, Brett Favre's struggles and the epic collapse of the Dallas Cowboys kept the public rapt, just as a stagnant economy forced more Americans to look for cheap entertainment.