I expect the Celts to lose to the Bucks in round 2 in 5 games.
Milwaukee holds home court and wins a tough one in Boston, drops the other Boston game, closes at home in Game 5.
The Bucks have the MVP, they have home court, and they've been the best overall team throughout the regular season this year.
The Celts have a decent roster to slow down Giannis; unfortunately they are likely to struggle to contain Middleton. I expect Eric Bledsoe will have some revenge, as well. If Mirotic is back that will be a problem for the Celts as well.
I think the Bucks can beat the Celts without Brogdon, but if they have Brogdon healthy, that just makes the matchup even more in their favor.
Bottom line, the Bucks have a SRS of 8.23 whereas the Celts have a SRS of 3.91. There is a huge gap between the two teams. The Bucks should win comfortably.