Posted By:
davidcycleback'Say Hey' is Willie Mays' company, and you should have no worry about the authenticity. If a player's hologram is on the ball (or jersey, other) it's safe to assume the signature is genuine. The player's whole market advantage ($$$) is that the hologram indicates the ball and autograph are from him.
Additionally, I've seen numerous 'Say Hey' hologrammed balls later get LOAs by PSA/DNA and JSA.