Psychology and athletic development

I have been very concerned recently by the concept of a player testing very well but not performing up to their testing results. For example the player who has a 65+ VO2 but fails to make recovery runs when the ball has been lost but this same player if they were doing a et of intervals would be leading the pack. I am interested if others have seen a similar problem with players still pacing themselves although they are conditioned to not have to worry about pacing. I have been very strong with this point recently trying to get players to trust how well prepared they are. I welcome feedback