The only position that we know is set is at Small Forward. Pierce will start. The battle will be for minutes behind him. Pierce had his best season last year and may be even better this season with a pure point guard to feed him the ball. The one question that we have with Pierce is will he run? Doc wants to run and run and run this season and hopefully Pierce will join in. Last season Pierce showed a willingness for the most part to buy into Doc's system and do what was asked of him. I believe that when he sees other players getting easy baskets by running with the point guards, he will happily join in the running game.
Behind Pierce, we have several players who, like Pierce can play two different positions. I expect Gomes to play some at the 3 this season since he has slimmed down and worked on his quickness and range. He may even play more at the 3 than the 4 if he plays well enough there, giving more time to Powe at the 4. The other player who should get some minutes at the 3 is Gerald Green. Many believe he will be sent to the DLeague but I think he will stay with the team and back up Pierce. If Doc plays small ball Tony Allen may also see some time at the 3 with Pierce moving to the 4.
Green showed a lot of improvement in the summer league. He doesn't look like a deer in the headlights any longer. His shot is as silky smooth as it always was and he shot without hesitation. He still needs work on his defense, but if he works hard with the coaches over the summer, he should improve even more by training camp.
There is no question that Pierce will start. The question is whether Green has improved enough to back him up.
No question about it; Gerald Green needs to stay with the team and not be sent down to the D-League. He proved last year when he was given ample minutes to play, that he has the confidence to already play at this level and succeed. And like you mention, his summer league performance was a good indication of his improved play. Defense will not be a strong suit for him yet, but as a bench player, he can hide it a bit.
Gerald's minutes will be determined by how ready his is to start playing against the big boys. Even if he doesn't play that well defensively, his scoring ability will get him some minutes on the floor. If he's scoring the ball well, he could force Rivers to use him as the 2nd guy off the bench (with the 1st guy being either Tony Allen or Delonte West).
If he's playing well, Gerald could get 15 mpg on the floor. He'll receive more as he plays better defensively.