Gobert is well on his way to being top 5 but doesn't have the longevity yet to be included there (in the 6-8 range right now). Paul Millsap and Mark Eaton are also both in the top 8 if the list extended that far. Next tier after that would include (in no particular order) Deron Williams, Mehmet Okur, Derrick Favors, Bryon Russell, Carlos Boozer, and Gordon Hayward. I assume Mitchell will likely be on the list once he's been in the league a few years but can't consider him yet given he's only in his 2nd season.