Russell will probably not be a very good defender, but who cares, we have Gobert and Favors down low. It's not like Steph Curry really plays defense, but he has Bogut and Green down low and Thompson on the wing.
Favors and Gobert are our Green and Bogut, and Exum is our Thompson (defensively speaking).
I don't think we'll finish low enough to get Russell though. He's solidly top #4 now. Better to not have your hopes up.