I admit that I don't look the skills of the players I want to buy, only their previous stats but I want to ask something.
I have the impression that all the older players after many games and training have skills like that (their light grey).
I mean an attacker has very high attacking skills and a defender very high defending skills.
Those skills are higher than a 6* (or 7*, recommended) player, young one, with balanced skills.
Only on prurpose, choosing specific drills you can keep a player with equal skills.