This move is as much about the short term as adding a vet for the playoffs. Who knows if Moore can turn into that vet, but in the next 10+ games, maybe more, muscle strains heal slowly sometimes, the C's needed another big off the bench. Since they cleared out POB and had his spot, with the KG injury, picking up Mikki was a no-brainer. This was not a multiple choice move of who is the best PJ clone for the playoffs between Moore and Smith, this was a move to address an immediate need, that may or may not pay dividends down the road.
If the C's believe they still need more punch for that playoff vet off the bench, they still have one roster spot and could create another one if they really wanted whichever player was available. Once KG went down, sans a 10 day contract player which Doc rejected, the simple reality is the Celts needed another big body right now to stay afloat in the meantime. The move needs to be seen in this light. If Smith and/or Marbury become available and Doc and Danny believe they are both essential as the playoff vets, they can pursue both of them at that time.