If Woy wants to get the most from the lad, seems he should have praised what he did on the pitch, then "although he could do a better job retaining the ball in some situations." - i.e. "You played a great game, but still have some areas to work on."
Give credit where it is due so as not to crush the spirit of the player, while keeping him aware there is still room to improve.
It is turbogash to neg a player who did a lot and praise those who apparently, by some of your accounts, slightly more effective than orange cones.