Porzingis or Mudiay.
Either would force changes in the rest of our roster, sure. But either would be a huge upgrade at their position (PF, PG) in talent. My preference would be Porzingis of the two, but I'd take either. Mudiay is a mystery man to a lot of folks but if you watch vids of him, his upside is pretty obvious. He could become one of the most explosive, creative point guards in the NBA. He's incredibly difficult to stop from penetrating to the hoop and he's got great court vision and is an excellent passer. Porzingis is potentially a tremendous scorer with both his ability to finish quickly to the rim and his great outside shot. And he's a very athletic defender who can block shots. He'd be a great fit for Stevens' system.
I also would not be averse at all to Russell, if he slips to #4. He'd automatically be our leading scorer right off the bat.
And I'd also be fine with Mario.
I'd be "OK" with Winslow, but this seems a bit high to be taking him.
This is definitely too high to be taking WCS, imho.
This is probably just a pipe dream, though (getting the #4 pick). And what would the cost be?