Wiggins maybe assigned to defend Jaylen Brown and Draymond Green's mission is to stop Boston's leading super star Jayson Tatum. It is unfortunate that Boston is facing a very experienced team in the finals. But everything is set. Boston should show that they are also good defensively and they can shut down Warriors' scorers. And that they also have enough fire power to combat Warrior's shooting.
They will be left with nothing below the paint if that happens. Looney may not be able to handle Horford and Grant Williams to take the rebound. If Draymond will defend guards then the paint will be left wide open for an attack or an offensive rebound.
They still have Klay Thompson and I am sure as hell he could defend Jaylen Brown. That will not be a hard task for him, they may also be a good match.
The fast switch will be the troublesome feat but GSW is used to it sugarcoating their weak side which is Steph but are the Celtics prepared if it will be the Warriors doing the same strategy. I wish they are.
I believe that when you look at it as "small ball 5" that will not be the case. Like imagine Curry- Poole - Wiggins - Klay - Draymond five on the court at the same time, obvious that Klay can't play the PF position, nor any other of the four there, Draymond can play C but there is no PF there, hence it will not be a common thing, but at times they can test that out when celtics have their own small ball line up.
Aside from that Looney will be 5, and Draymond will be 4, and that's it, they will defend their own positiosn, maybe with some switching but that's it, they have done it before and they can do it again, they even got outrebounded but still managed to make it work.