Playing with only one player on defense is hardly a coach mode way of doing things. There are many of us that just pick one player. I used to think it was cheap when guys would always switch to different guys. Its like they would just screw up the guy they are playing with and then switch to a guy who's in a position to make a play.
I personally like to stick to the player I use which changes during the game, and carry out my assignment. If I get beat, that's fine. If my CPU teammate gets beat that's fine too. It makes it more rewarding when I get user picks, sacks, tackles for loss because I know I was responsible for 100% of it. I just didn't switch at the last second to a guy who did all the work so I can get the glory.
I really don't have a problem with people who switch but don't assume those that don't just want to sit back and watch the action.