Maybe you're right about tackling.

3 seasons ago, I saw, my defenders had really low tackling-skills (to train "only" tackling isn't that easy) . I thought, maybe that's the reason, why opponents had a very high shot to shot on target-ratio (f.e. 9 shot, but 6 SoT). So trained all new defenders high tackling (best or second best stat). This season, all defenders together had 76 appearences, but only 2 yellow cards - and that's my DL, who has the lowest tackling-skill, but also the highest aggression.

The player, I descriped, has average tackling-skill.