In the NFL revenue doesn't have as big of a spread as MLB has.

According to Forbes the spread in 2005 revenues for MLB is from $264M (Yankees) to $80M (Nationals). The NFL has a spread of $287M (Redskins) to $153M (Cardinals) for 2004. A difference of $126M is nothing to sneeze at, but it isn't as massive as the difference in MLB that allows the Yankees to spend massive ammounts compared to the poor clubs. The NFL shouldn't suffer from any Steinbrenner types because even the poor teams are making enough revenue to afford a player or two.

Basically, the NFL doesn't need a salary cap. Green Bay, Tampa Bay, and Tennessee are small market teams that manage to do well in revenue, so obviously small market teams can make money. Teams need to find ways to make money and use it wisely. And even then deep pockets only go so far. The Redskins went out and bought a bunch of top free agent talent a few years ago and failed miserably.