From profootballtalk.com

A really good article and a good read...puts the whole idea of NFL games on the NFL Network into perspective

MAYWEATHER-DE LA HOYA AND NFL NETWORK by Michael David Smith
Floyd Mayweather defeated Oscar De La Hoya Saturday night in the biggest fight in years. [Editor's note: Zzzzzzzz.] But even the biggest fight in years was viewed by only a few million people -- nothing compared to the size of the audience the NFL draws.
The reason, of course, is that Mayweather-De La Hoya was broadcast on pay-per-view, just like every big fight. Boxing has suffered a huge decline in popularity and become a niche sport because when fans have to pay extra to watch a sport, many of them find something else to do.
And that brings us to the NFL's decision to begin showing games on NFL Network, which tens of millions of cable subscribers still don't have. The business dynamics of the NFL putting its games on its own cable channel and boxing putting its fights on pay-per-view aren't the same, but they're similar: A sport has decided to make more money and have more control by putting its product on a platform that fewer fans will see.
Will the NFL decline in popularity because of NFL Network? Not any time soon. The package of games is limited to eight Thursday and Saturday nights, and the NFL wisely shows games on broadcast television in the markets of the two teams playing. If anything, the overall existence of NFL Network has helped the league's popularity.
But the current slate of eight games is as far as the league should take it. The NFL needs to resist the temptation of trading a smaller audience for more money, unless it wants to see its popularity go in the direction of boxing's.