I'm playing a complete Bundesliga Squad and used so far: Süle, Min Jae, Upamecano, De ligt, Schlotterbeck.
Nico Schlotterbeck is by far the best Defender of all of them. And he is also not very expensive.
I used him with shadow chem style.
I guess what makes him that good are his playstyles, he's got everything a IV needs in my opinion.
Only thing that makes him a bit difficult to play, is 2* Weak foot, so be sure you keep that in mind when passing the ball ;)
Pace: 8/10
Shooting: 9/10 (almost every header gets on goal)
Passing: 6/10 (not the best but decent for an IV, be sure to use his left foot)
Dribbling: 6/10 (like passing also decent)
Defence: 9/10 (Wins almost every duel or intercepts the passes very well)
Physics: 9/10 (Very nice stats in this one, i guess only Haaland and these strong physical strikers can play him out in this stat, every other attacker should have no chance)
2* Weak foot
Passing + Dribbling decent but not the best.