We have talked to some length about Hezonja, who is a big possibility given our lack of SF depth. A couple of other options that stand out, particularly because they are young and UFAs, Kevon Looney and Jerami Grant.
Both players are only 22 and 23 years old, and would be logical targets to help improve athleticism in the rotation at a low cost. Either player could see the opportunity to start here at PF in the absence of Porzingis at the beginning of the year, but even when Porzingis is back, either would fill the role of backup PF and play alongside Porzingis when he slides over to center. So the minutes and opportunity will be there.
I am guessing that Hardaway may see a lot of SF minutes (and even start there) with Ntilikina and Mudiay in the backcourt. Drafting Mikal Bridges and using him as a 6th man in his rookie year, along with the possibility of bringing back Williams if he continues to impress, would improve SF depth, making the PF position more of a need. We won't be a better team next year, but we need to get more athletic, younger, and better defensively, and adding Bridges in the draft along with a FA like Grant or Looney would go a long way in doing that.