Yup, Jonathan nailed it, it's Andy Phillips.
I thought since Mattingly and Pettitte were teammates (as players) only in '95, it must've been someone from that team.
But Andy Phillips was a Yankees from '04-07. Pettitte was on the '07 team, and Mattingly was the Yankees bench coach that year. And this card on ebay shows the same signature. Well done Jonathan!
https://www.ebay.com/itm/15738402661...id=16055928147