I think Green is clearly a better defensive guard than Miller or Williams, let alone Ivey. He's also a better shooter than Ivey. With Thad out, I would have liked to see Willie try to drive to the hoop, and generate assists, which he has started doing.
The Sixers defense does not stay with their man. That's why these other players get open. They should stop helping so much and that would do more to pressure their style of offense- they're not particularly good off the dribble, so jump on their passing instead.
The Sixers lacked enough offensive punch, and had too little defensive stopping power. They were doing better when Speights was in instead of Evans. But Ivey and Ratliff kill them when they're on the court.
We really need another SF, Center, and a PG replacement for Miller who's really starting to mail it in.