Play a full season with your favorite team or try the franchise mode and build a legacy. You can even create teams and players.
In general manager mode, when you go into the off-season, several different things happen. First, you'll see a list of players who have retired from your team and the reasons they've left, which are usually related to injuries or diminishing skills. If you lose some key players, then you'll need to make every effort to ensure that those positions are filled by free agents with similar skills or rookies who have solid potential. You're frequently stuck with trying your luck in the draft, where you can select a rookie based on how you finished the season, like in the real NFL draft. GameDay has a feature that gives you a breakdown on the draft and provides you with an overall rating for each rookie. Following the draft, you have to sign your rookies with whatever cap money you've set aside for that purpose. When you're all done, it's time to start the next season.