Regardless of what the coach is saying, first you need to assess the player quality for yourself. As stated above, the text is based on the scout report stars. It means the player is good/very good at something, but that doesn't mean he won't be bad at some key skill that is not described on the scout report.
When you are sure that the player is 'top class' (or if you just want to gamble or give him a try or whatever), you can:
- Send them to training camps every season so they can train faster and earn more balls while there;
- Hire coaches to help their development outside training camp;
- Let them play lots of league matches and/or friendlies so they can earn experience and have 3 experience balls when they turn 19 (this is not really required, but adds value to your player);