This is the proper way to do a 3 back system. but make sure that you have enough backs. I did the auto sub thing in my FAU dynasty. My first two running backs left the game and never came back. And after halftime my 4th string back was the only one getting touches. I tried resetting the auto subs and they still didnt returen. As you can imagine this is not ideal in year 2 of FAU dynasty.