I wasn't able to participate in the last few weeks of the SFL, and the playoffs, which I eventually won, because I couldn't figure out a league file problem. Based on my experience, the following happens:
[b4a67082]Players[/b4a67082] - The AI will play what it thinks are the best players. In the event of injury, it will make inactives active, but it will also scour the FA listings and sign a replacement, if necessary. This is the part that can screw you up if you're not careful, in that there may be a player [i4a67082]you[/i4a67082] think is important (often for the future), but the AI views them as superfluous, and cuts them to make space for a 4th RB because your #1 RB is out.
[b4a67082]Gameplans[/b4a67082] - Starting with the first week you don't submit a stage, the AI will begin controlling your gameplanning & depth charting.
Hope that helps!