His game shape will probably drop.
If you keep your players between 50 and 80 minutes, over time they will either have strong or proficient form. At that level it seems to be pretty random. If they are strong, they will be strong or proficient the next week, and if they are proficient, they will be proficient or strong.
Go outside that range, and you may see drops, especially if a player consistently is outside the range. A player might go 35 minutes and stay strong, but a 2nd week and you are sure of a drop. I had a player go 102 minutes because of a 2 OT game, and he dropped from strong to average.
A player will perform a little weaker. He may also have trouble getting playing minutes because he gets substituted out because of his game shape. That is where it is more likely to have an effect on training - because of low game shape, a player might get less than 48 minutes, and not get full training, and his game shape might not build up.