I think C's in 6 PROVIDED Shaq can play some limited minutes to provide fouls on Bron and Wade drives as well as allow Doc to use JO to back up KG on Bosh AND Green can provide solid, quality minutes guarding Bron and some much-needed bench scoring.
I think Bosh will crap all over BBD during the series and the Stern-led refs will give Wade and Bron a parade to the free-throw line resulting in foul trouble for Ray and PP.
I think Krstic can actually help in this series since the Heat don't have a really physical center and his shooting will be really helpful off the bench. Having watched Rondo against the Knicks, I think he goes off on the Heat more than he did against the Knicks. Spoelstra probably moves Wade or Bron to cover him and lives with Miller on either Ray or PP (and we hope they're able to play and not riding the pine with fouls).
If no Shaq, C's still take it but in 7.
If Green doesn't make a real contribution at least on D, I think the Heat could pull out the series. This is the team Ainge wanted Green for -- he's got to show up, play hard and really contribute.