I don't know much about Orien Greene or Mustafa Shakur as players, so I'm turning to those who do for help. First up, Greene as seen by a Celtics fan. Orien played 1,200 minutes for Boston in 2005-06, so C's fans have certainly seen him more than any other NBA fanbase.
Here's Jeff Clark of the famed CelticsBlog:
On the other hand, he was a defensive minded, pass-first point guard, and that goes a long way in my book. The problem was he couldn't hold onto the ball either. Think Rajon Rondo with Crisco hands. We had Delonte West, drafted Rondo and traded for Sebasitan Telfair, so Greene was an easy cut in a numbers crunch. It didn't help that he was caught going 90 on a city street.
I wish him well, I always pulled for him. On the other hand, even when the Celtics traded away all their backup point guards, his name never really entered my mind as a guy we should look into. He might be a nice find for you guys, especially if he's working with Thorpe. And if he doesn't pan out, the risk isn't that great.
As we've said, Greene has two things worked for him here: 1) Geoff Petrie has repeatedly gone for defensive-minded backups behind Mike Bibby, and 2) Petrie seems to have some deference to players connected to Thorpe since Kevin Martin exploded. But really, what settles this positional battle will be who plays better in preseason and who goes harder in training camp.