I have been wondering why my team seems to be playing below expectations. It appears that I have made a crucial mistake.

I allowed many of my players to achieve a level of 20 in Stamina. I have now found out that doing so causes a bug in how your team will perform. Instead of allowing the player to play better for longer, making stamina 20 causes the player and the team to play much more poorly.

I may have to cut them all and replace them.