Its complicated.
At the beginning of each game, the pitcher is assigned a pitch count (we dont know what that is). He also starts out at F9 (strongest) and as the game progresses may drop down, with F0 meaning he is pitching like I would. He will start to drop as he nears the pitch count. But if he is throwing well, he can go beyond his pitch count without becoming fatigued. (I said it was complicated)
I would suggest going here and reading the section on pitch count fatigue. I could reiterate it here, but its complicated.
https://stratomatic365.fandom.com/wiki/ ... nt_Fatigue