Posey was a luxury to have in 2008, but he's not the same player anymore, at least from an offensive perspective. He's lost some of his speed and shot pretty terrible %'s this year - FG's= .365% and 3PT% = 35%.
Sure he may have played better dawning a Celtics jersey but I like the specialization of each guy now as opposed to the "glue guy" we had in Posey.
Tony, Baby, and Sheed and Nate all combine to have the skill-set of Posey, but obviously each of them is not as talented at both ends.
Tony gives us hustle, D, and some opportunistic offense
Baby gives us toughness, rebounding, and offense
Sheed gives us toughness, D, the 3-ball, and 6 fouls to use
Nate gives us some instant offense and pressures the ball on D up the court - oh and some much needed SWAGGER from the bench as well
When Posey got in foul trouble we had the luxury of having PJ come in, but now we have Sheldon which many feel is a huge drop-off/difference, but I think Sheldon can come in and play fundamental basketball and use his fouls wisely should he get called upon in the finals due to injury or foul trouble. Call me crazy but I believe Sheldon is servicable.