During franchise mode, you can easily increase the room under your salary cap. First, look at some of your players with very high salaries. Some of those players will be very skilled, and some will not. It reflects the real salaries that they receive. Cut that player from your roster. That player will go into the free agent pool, where you can usually sign them for much less than they were paid before. However, you must be careful. Sometimes the player will demand more than they used to be paid.