Marion has been playing pretty well latekly. Last season he was a fantasy team all star with his statistics and has begun to return to that level this year. He scores, rebounds, gets steals, and plays pretty good defense. Marion really needs a team that runs, moves the ball around and uses him as a cutter.
I don't see Shawn at #2. He is not an especially good ball handler and it takes away from his primary strength which is that he is a great leaper. Instead, if Zarko proves to be as good as most of us hope he will be, Marion may become a "sixth man" which will mean he will see more minutes at PF backing up Amare.
What the Suns need at off guard is a pure shooter to compensate for having so many guys that are better at attacking the basket. Penny and JJ are clearly not pure shooters who are automatic whenever they are open. Casey has the potential, but may not be quick enough to make his own shot.
Barbosa might become the guy once he gets the experience. He is qucker than anyone else on the Suns and has an enormous wing span which means he could become a great defender. His shot is ugly, but it goes in. If it becomes clear that the season is a lost cause, I would like to see Barbosa in the lineup a lot.