I've found recently that when jockeying defenders to get position on them, I constantly hold jockeying and then press sprint to get back into position if they are getting away from me to get back into position, whilst holding the jockeying button still. I do this because when I let go of sprint, the jockeying kicks back in instantly and you can keep position on the attacker alot easier and tighter.
Before I used to take my finger off jockeying when sprinting and vice versa when going back to jockeying, which causes a slight delay in going back into jockeying. It causes you to slightly over run the attacker when sprinting and lose position easier because you don't have your finger on jockeying instantly. Your sprinting longer than you need to, which makes changing direction slower to keep up with the attacker. It's improved my defending without a doubt. Much tighter, closer and responsive to the attackers change of direction. I'm making alot more tackles comfortably than I was as I've better positioning now. Give it a try!