I think Theis is the best for the job for a few reasons. Maybe the most relevant is that whoever is on Giannis is going to rack up the fouls. Then on to the next.
They are going to need to double Giannis in sets anyway, or at least some form of rotation. And there are also going to be a lot of switches. I would rather see Horford on Lopez than on Giannis. Don't need to have Horford picking up unnecessary fouls.
Grant Williams will probably get the secondary assignment on Giannis. RWill on Portis or Lopez. Neither of these guys can stop Giannis one on one so it doesn't really matter. May as well let Grant take him.
You want Theis on him BECAUSE he'll pick up fouls? That's... an interesting take.
Yes, Giannis is going to get every call no matter who is on him. I would rather Theis get into foul trouble over Horford, for example. We will have combinations of bigs on the floor, if Theis is on the floor, he should be the primary Giannis defender. Next up is Grant Williams. At times (hopefully fairly often), it is going to be Horford and RWilliams on the floor. In that case, Horford can take him. We don't want to get to the end of the game and have Horford and RWilliams in foul trouble. Better to have Theis and GWilliams save them from fouls.
I agree with the ethos of this. I think Theis (foot speed) and GWill (strength) will be the main primary defenders of Giannis, with Smart, Jaylen, and Jayson as ideal switch candidates and change-of-pace primary defenders for a handful of possessions a game. I expect to see Al and Timelord playing a quasi-zone and hanging back to double or be a second line of defense most of the game. Giannis is a bit tougher because he
will get into the paint, unlike Durant, who could be slowed down by Jaylen/Grant/Tatum's strength. On the other hand, you don't have to stick to him 35 feet away from the basket. I expect to see a bend-don't-break D from the Celtics as opposed to the chippy, all-denial one they played on Kyrie and KD.