Has he produced in the past? Who is telling you he is doing it at practice? If he is of the age where he is away from home and on his own (hopefully he is 18+) he needs to figure out a way to be in the line up. If not producing - be the best penalty killer of face off guy on the team, just do something at an elite level.
I have coached and taught players for over 20 years, and have had great success with sports mental training. There are several online classes, and most of them state that it is very common for a player to perform better in practice than games since there is no pressure, fear of failure, expectation, role, or consequences. Most classes teach very simple thought techniques to correct this, at any age and level, even professional. Good luck.