That's what I was thinking. I remember reading somewhere before, and I read a lot of articles, that when your sprinting your jukes and spins and break tackle moves that make your RB evasive are not as effective. They said to not sprint into the line but rather coming out of the hole. Sorta like you slow down enterring a corner and speed coming out of one in racing. I guess I'll keep my auto sprint off because I want to be able to break tackles when I'm running inside and you can always press RT (It's a habit for me anyways) and use speed that way.
BTW I've become accustom to hold down LT and manually strafing so I think I'll keep that off as well. I find your able to turn and run faster with it off when your not holding down LT to manually strafe which allows for me to get to the ball quicker. It takes more practice to do effectively and I sometimes am out of position on coverage and the ball goes over the top of me but for the most part I just gotta practice and get better at it.