I thought were were past this myth already. The Spurs plug and play new players whenever it makes sense. Sure, new guys don't always get big minutes, but that's more a function of the team already having a strong rotation rather than their system requiring a long time to learn. Whenever there's a hole in the rotation, new players fill them rather quickly. Neal played stable playoff minutes his first season. Green was a starter during the 2012 run his first full season. Kawhi, obviously, and Diaw even more.
I disagree with Harlem that STAT wouldn't be able to fit with the Spurs. I think the bench could totally use a strong post scorer. The Spurs need some reliable points from their bigs, and only Tim seems able to provide them this season. Even with the defensive issues, it seems clear to me that Amar'e would have a ready-made role on the team, and that's more critical to his sucess than play knowledge.