Value is best indicator, for level 3 and 5* player I think 4-6 M. I remember in my first season I bought 5* player, 19 years old, 2,2 M. So your player is slow trainer. Try to find boot players (you can easy detect them, club names always have AC or FC and it's like FC Liberty, AC Ghost or Love FC), they are very rare but sometimes I can find them right after maintenance.