Nate and Sheldon, the two lowest +/-, did what they are asked, so you can't complain there.
Here's the trouble with single game +/- stats. I'd argue Nate played exceptionally (again) under pressure, in the crucial minutes of a one possession game at the start of the 4th. Hit a 3, drew a foul on Bynum, hit his free throws, protected the ball. I want Rivers to find him first half minutes from here on out.
While Shelden looked lost with the Celtics up 12 at the end of the half, an MIA dunk, failure to hit the floor, sloppy momentum killing turnovers and a blocked attempt. His per36, to throw out another (semi-)advanced metric, 0-9, 9 Rebounds, 18 TOs, 18 Fouls. I'm not sure I want to see Williams in meaningful minutes again this series. (And I didn't want to see him in the first place. Phil let Kobe close out the half with four fouls and look what happened...)
EDIT - Second guessing myself on hammering our 13th man, let's say, maybe tomorrow I can forgive him for not falling on a 50-50 ball and that SECOND turnover - since we won.