Spoelstra was already thinking along the same lines as Roger; since they couldn't defend Nowitzki, they decided to remove one defensive point and add a point for organization.
This season, because Boris Diaw had gained weight like a ball and couldn't slim down, it severely affected his speed, so he could only play as a power forward, unable to switch to small forward, let alone play as a guard like he did early in his career.
This greatly limited his role.
But his technical characteristics remained unchanged; he was still the guy who could embellish the offense.
Without Brandon Roy, Boris Diaw could also temporarily supply ammunition for Roger.
As for defending Nowitzki? Since neither Stephen Jackson nor Matt Barnes could stop him, it would be better to set up an additional point for ball handling and control to create off-ball opportunities for Roger, allowing his firepower to compete with Nowitzki's.
