Pitcher over use and fatigue in mystery leagues

I can’t find good explanations of how pitchers are penalized for over use in the mystery leagues. I am aware of the super reliever issue where relievers can get used a lot without suffering fatigue. But what about starters who also relieve?
I’m in the playoffs and I want to use starters as emergceny relievers. Can I do so without hurting their fatigue level when they start in 2 games? Or will Hal not let them start that game?

I do not think HAL will use SP/RPs in relief if they couldnt start that game. However, HAL will use a SP/RP as a starter a day or two after it was used in relief. I am not sure how fatigue works in those situations, my my gut says there is no extra fatigue.