To SELL he needs to be signed. He's 19, right? So either 1st day youth or last season -- plenty of time to play him. Many people sign the youth, play him a few to see how he is (or get him closer to his next star.) The freebie youth from levels above have near the value of a fast trainer but are ducks. They can also be good players with above average training rate. On a couple of my Teams I have kept them for over a Season because they play well.
Player ratings I believe are related to how often they are expected to interact with the ball vs. how they did in the match, and scoring has little to do with it. I still think GK ratings are not as useful as field players.
After 22 it can still be worth Training, especially in their happy place. I have had 26 y.o.s do as well as youngsters in their favorite type of training.