If you look more globally, Spurs roster is split apart this year. On the one hand there are 9 quality players with Parker, Mills, Belinelli, Green, Ginobili, Leonard, Diaw, Splitter and Duncan. On the other hand, there are some bad players with Joseph, De Colo, Bonner, Ayres and Baynes . The gap between these two groups is quite huge.
It's really nice to have a quality depth of 9 players but 10 would be perfect. When you look at this 9 players roster, a mobile PF or big SF would be the perfect complement.