Spurs. The answer to this question, no matter the player, is always the Spurs. Celts are closing in that distinction too.
This long held belief may be destined for the trash heap of history. As currently constructed, the Spurs are a great landing site for any player, because it is such a well run franchise.
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But, if Kahwi leaves and Pop retires....IDK how good a situation it will continue to be. It was an incredibly well run franchise, but a lot of luck went into it. First, they draft the Admiral. Then, just after the peak of his abilities, he sustains a unicorn of an injury, one that effectively sidelines (or gives the team a viable reason to sideline) him for an entire season while having no long term negative impact on his abilities. Then they win the second most important NBA draft lottery ever, and draft the most pro ready player of the last 2-3 decades in Tim Duncan.
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In subsequent drafts they took absolute flyers on Tony Parker and Manu. TP was an absolute flyer, and lots of people questioned if Manu was all that interested in playing in the USA. Both came over, and dominated.
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Then they drafted Kahwi, mostly in the hope that he'd be able to ably defend the plethora of wings in the western conf (with LBJ waiting in the finals). They hoped he'd be in contention for DPOY awards without being a complete wasteland on O. Instead, he blossomed into a top 5 player in the L.
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They obviously had some smart moves. But even those smart moves turned into players that WILDLY outperformed even the most optimistic projections.
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But take Kahwi and Pop away from the Spurs, and they are just another small market team stuck in Draft Lottery Hades.