Ok. I think I already had tweaked the midfielder instructions to minimize the gap between midfielder and defender. The tactic has 2 midfielder. These two midfielder have a different function. One is cover defense as a MCd and one as react to get the ball and supply to winger or striker which we call as a MCa. Both of them have same mentality which is "Normal". But the other attributes is different.
So, the defender that you need is likes Ferdinand and Vidic that I used at Man Utd. Other are Sakho, Mexes, Fazio, Marcano and other that have high attributes of tackling, heading and marking.
Mate, if you want to see the instructions, try to download my latest tactic, Man Utd 9.3.0 v7 One or you go to the page 6 of this thread. Btw can you post the screens of your line up? Maybe I can help you.