Right now I would argue that the best defensive player in the NBA is Rudy Gobert - we just need a larger sample size. Duncan is a 2 way player for sure, and he is having another really good season. However, there are a lot of things Duncan can't do anymore and at times he can be a liability. Popovich benched him in the final minute of the Heats 2nd title because Duncan wasn't mobile enough to guard a shooter, which ultimately cost the Spurs the championship.

I think Duncan is close to 10 but there are about 7-8 guys in that category that I wouldn't list in my top 10 but I could easily argue for each one to be in the top 10. guys like Aldridge, Duncan, Leonard, Lillard etc...

Curry
Harden
Westbrook
Lebron
KD
Anthony Davis
Chris Paul
Marc Gasol
Klay Thompson
Blake Griffin