Ai Defenders are useless

I play on ultimate, just got West Brom to the Orem and my defence isn’t the best but why can’t they fucking run??!!! Every time a winger skins my full back the centre backs just jog back or stay still and let their man run past and it’s an open sweaty every time. It’s terrible if they at least ran I wouldn’t mind but they sit there and do fuck all they don’t bother tracking back and it ends up being a 3 on one all the time. Tried playing a 5 back to combat this and it didn’t help one bit