When the 2011 NFL collective bargaining agreement was first reported on, a clause on a minimum spending rule was often included. Teams would be obligated to spend 89% of their salary cap space. This isn't really what's actually in the CBA, however, but that initial reporting has stuck in people's minds, thereby creating a lot of confusion on what teams have to spend.
So, let me clarify these rules again, because I end up doing so every year. To make it simple: NFL teams don't have to spend 89% of their salary cap. The salary cap floor does not apply to any single season, only to the entire 2013-2016 period. That means that not being in compliance in any single year is not going to be a problem for any team. Only if a team has so chronically underspent that they managed to still be below 89% over the entire four-year period, will they be held accountable.
Even so, there's no additional punishment beyond "spend the extra money." If the team hasn't spent 89% of the salary cap over that period, they'll have to fork over the difference to the NFLPA after 2016. That's not ideal, of course, but it's not exactly a huge incentive to just overspend, either.
So are the Tampa Bay Buccaneers on track to spend 89% of their cap space? I don't have the exact numbers, but we can make a pretty rough estimate. Over 2013-2015, the combined NFL salary cap totals $399 million. The Bucs currently have $30 million in cap space -- and that's likely to be very close to the amount they find themselves below the total cap, given that the Bucs have carried over all of their open cap space in the past years. In other words, the Bucs have spent $369 million of the $399 million cap space, or 92.5% of the total salary cap. They're not in danger of being forced to spend anything, any time soon.
In fact, this is likely to be a significant underestimate, because the Bucs carried over some $8.5 million into 2013, which means that some of the space they have now is a result of pre-2013 cap space, which has no impact on the NFL spending floor.
In other words: no NFL team has to spend anything this year if they don't want to. They might have to do that after 2016, but even then the penalty for not doing so is non-existent. And even if that were an issue, the Bucs are pretty comfortably above the spending floor anyway.