The easy version of this story is to stop at Joel Embiid being unavailable. The more useful version is that Philadelphia has already shown what the first answer looks like. It is not one replacement center. It is a split.
Andre Drummond gives the Sixers bulk, rebounding and the kind of possessions that keep a game from getting away. Adem Bona gives them something different: activity around the rim and a little volatility in a good way. When Bona had three blocks against Orlando, that was the sort of playoff cameo that changes how a bench option is discussed. He stopped looking like a placeholder and started looking like a function.
That matters because Boston is the kind of opponent that turns vague rotation ideas into very concrete tests. Philadelphia does not need Bona to impersonate Embiid. It needs him to make short stretches playable. If Drummond can handle the heavy work and Bona can supply rim protection, the Sixers at least have a center committee with two distinct jobs instead of one impossible assignment.
Nick Nurse's praise of the emergency tandem is notable mostly because coaches do not have to frame these situations that way. He could have treated the arrangement as survival. Instead, he pointed to real competence. That does not make the matchup easy, and it does not erase the loss of Embiid. It does, however, make Bona the interesting part of the problem.
For Philadelphia, the question is no longer whether the rookie can fill in on a desperate night. The question is whether he can keep giving the team a few possessions of verticality and shot deterrence that let the rest of the lineup breathe. In a series that begins with reduced options, that is already a meaningful job.