Friendly or training regime best for gaining skills?

[Raykco]

unfortunately for me, it's always the same player that gets injured. 4 times in 1 week now for him.
Worst thing is, he's my best player. My only young 5 star guy (striker too).

Makes me wanna quit playing lol

If the player has been injured 4 times in 1 week, it sounds like you use red packs to recover him too quickly. Try letting him recover normally and see what happens. I hardly ever use packs to heal injuries.