I think Doc Rivers takes the reasonable stance of not trying to work on too many projects at the same time. Since Crawford and Williams are the ones signed beyond this season (and also the more talented), it makes sense that Doc work on them first and try to get them to play his way and integrate them into the rotation. Once he's figured out how much he wants to play with those toys, he can move onto the next two.
Until Doc is to that point, then White and Randolph might be used situationally, perhaps only against teams where he thinks smallball is never a viable option.