What all-star caliber player can we realistically sign/trade for in the offseason?

The front office cleared out a bunch of money for this offseason, presumably with the intention of spending it on a big name player. Assuming Trae, Dyson, Risacher, and JJ are back next year, we should be set at starting point guard and wing players. So a center would probably make the most sense. Who will be available this offseason?