You can borrow from future years cap to add cap this year, that is what is happening. If you do it somewhat responsibly and the cap goes up (the NFL grows) then you can get away with it. If you are a drunken sailer it will catch up with you in a bad way eventually. Teams go through "resets", etc from time to time, the Bills did that in Allen's rookie year. Fans and sometimes GM's play the role of spoiled brats who demand their parents go into lots of debt to have all the toys they want today. This all reduces what is possible in future offseasons.