Because Zito throws so soft, he's scared to throw fastballs over the plate in fastball counts, like to start the at bat. He often falls behind hitters. As a way to combat this, he likes to throw that big slow curve to steal strike 1, and because batters never sit offspeed on the first pitch, and are usually taking the first pitch anyway, it works for him every time, and he never gets burned.
But if the Tigers want, that can end. Zito loves throwing that pitch even to righties. Miguel Cabrera, that curve is going to drop right into his happy zone. If he's ready for it on the first or second pitch of the at bat, it can be like batting practice. That's your early lead right there. And that goes for every hitter. Sit on that big "get it in" curve and actually swing at it unlike everyone else, and you can end Zito's night before it even begins. I'm telling you, it's there, big time.