KG has been a center for a couple years now. His move back to PF this year was an utter failure, and I think if Lopez was healthy enough to come back during the year, given the success w/ small ball there's no question KG would have moved to the bench rather than Pierce or Livingston.
Moving forward I don't think KG will be a starter (which you can obviously see in his rating). Pierce is likely done as a Net and will go back to SF with whichever team he joins (likely the Clippers), however I don't think Joe Johnson is moving back to SG anytime soon. We could see Teletovic as a starter, or perhaps a FA replacement, but I don't think it wise for the Nets to run with a Lopez/KG lineup again.