Ballo is the best true center in the Big Ten by a wide margin, if they go by positions and not just the top 5 players. His only competition really is Ivisic for Illinois and Bittle for Oregon, but it's too early to tell. Dawson Garcia is probably the best player capable of playing center, and maybe Owen Freeman if he keeps this up, but Ballo is really the only proven true center right now.
But Mack probably has the best chance to make the All-B10 team because I think he can keep up this 20+ ppg pace.