But
dirt is not foreign to the ball. Spit is a completely different thing as is Vaseline or using sandpaper.
Are we going to start making the pitchers wipe off the ball every time it touches dirt? If that's the case, I'd still be umping my very first game because that's how long a game will last. I can be given two brand new balls at the beginning of a game and prior to the first pitch of said game, I'm quite certain one of those balls has seen the ground and the other ball that's still in my ball bag is going to have some kind of "foreign" substance on it whether it's dust or residue from a dryer sheet. Don't get me wrong, I'm not saying a pitcher can take the ball and rough it up in a pile of dirt that he/she has conjured up but if he/she puts some dirt one his/her hand and doesn't wipe their hand on their pants/shirt, I'm not calling IP because there's nothing in the rule book to back it up. Just so we're clear, IMO dirt is
NOT a foreign substance and unless they're using mud, the dirt isn't sticking to the ball in any way that will change the flight characteristics.