Still a few weeks left in the season, but to me, the choice is between Renfroe, Whitlock, Hernandez, or Eovaldi (based primarily on the fact that he's been the staff workhorse, something you couldn't have predicted at the season's start). Strong arguments could be made for any of these candidates, but I'm going to go with Renfroe because I'm a "what have you done for me lately" kind of guy.