You have to play Lopez because he’s an elite rim protector and as you saw in the Brooklyn series the Celtics could simply drive to the hoop at will because the Nets had no one to really contest shots or keep Boston off the glass offensively.
The other factor is Lopez will force them to honor his 3pt shot. It’s tougher to “pack the paint” when you have bigs like Portis and Lopez that can consistently hit their outside shots.
If the Bucks can continue to get contributions from Allen and Pat C I think Milwaukee has a real chance to take down Boston even without Middleton. The X factor to me is how the refs treat Marcus Smart. If he’s allowed to flop and draw charges the Bucks will be in foul trouble and that’s the one area that they can’t have happen.