I didn't see the game, was Collins needed against Duncan?
I don't think Collins was worth playing against Splitter or any of San An's other bigs. Better to stay small with Bass and Wilcox. I don't see what Collins would've added.
I view Collins as a third string center. I don't think he is talented enough to help this team in a 15mpg role. I think he needs to be a situational sub who is called upon when a quality center is on the floor while KG is resting and/or when Doc wants to go big against a power-based lineup. Short of that, keep Collins on the bench and play small lineups with Wilcox at center while KG rests.