This year the NFL is allow teams a "carryover" salary cap in which unspent 2013 salary money can be spent in 2014. Last year Joe Banner of the Cleveland Browns underspent the salary cap by $24 million dollars which gets added to the Browns 2014 figure. So all the NFL teams are allotted $133 Million dollars this year, but the Browns can actually spend an additional $24 million, or up to $157 million, if they want to. In other words, the rules are set up to allow the Browns to overspend in 2014 because they underspent in t 2013.
However, the Carryover money is sort of like a savings account. Once you spend it, it's gone. If they were to spend $157 million this year, they would be obliged to cut back to $133 million next year. I think they are going to wait until they feel that they are legit Super Bowl contenders.
It might also be mentioned that if players and their agents knew that the Browns were going to underspend in 2013, probably free agents would have been less inclined to sign with them. They got away with it once, but in my view it was the right thing to do to let Banner go, otherwise what free agent would ever trust the Browns again?
Would the Browns be able to sign a Free Agent like Paul Kruger, if he had known in advance that they planned to tank the season to the tune of some $24 Million?
As it is, right now (June 2014) they are about at $133 million, which is their annual salary cap "allowance." They could try to sign a player or two if there are some guys who are cut by other teams with cap problems. The Browns could carry an expensive player if they want. They could also create some additional room by trading Ahtyba Rubin, who is a very good player, but who also has a very big salary, with most of it not being guaranteed.
The Browns have fared very well this year because their GM, Ray Farmer, has understood the rules better than his rivals. For example, by giving Andrew Hawkins a front loaded deal as a restricted free agent, the Bengals could not match it because they did not have the 2014 salary cap room.
Browns GM Ray Farmer has been brilliant this off-season, by manipulating the salary cap rules in favor of the Browns.
Similarly, Farmer was able to get a multiyear deal done for Pro Bowl center Alex Mack, by manipulating the Franchise Tag (or Transition Tag) rules. At the beginning of the off-season, the sportswriters were saying there was no way that the Browns could sign Mack to a multiyear deal.