i'm surprised i haven't heard this, since THIS is really the example you'd want to use it on.
Diaw knows D'Antoni's system with Nash and knows what D'Antoni tells them to look out for and what kills some of the system. this isn't like a Michael Finley-Dallas departure or an Eddy Curry "Mavs want to know stuff about the Spurs so they sign a scrub" deal. Diaw was a main point in D'Antoni's offense and coached him on how to run the ball.
Diaw's input on his old coach could be significant.