No. Stamina effects how long a player can play effectively in a game and only that. If your player is averaging 42 minutes a game then that means that he is playing 84 minutes+ per week which is way to much. That is why his game shape is lower than you'd like. Try to get him under 70 minutes per week and it will improve his gameshape.
Murray/Harris/MPJ/Grant/Jokic - 2020 NBA Champs