Since the minimum target pitch count is 40, if a guy can throw 40 pitches he can start. I've even used guys like
Player Profile: Francisco Quintanilla in a pinch if I need to.
Also, if you need to start a reliever who goes less than 40, set him into the next starting spot (for example SP3 when your SP2 has the ball), then once your reliever gets the ball for the next start you can move him to LRA and you can now set his target/max to as low as 5. After this game SP1 automatically gets the ball next