The Boston Celtics went into the playoffs unsusre of exactly how good the could be. They knew they could do damage with the three point shot, and had one of the truly elite defenses in the league. The problem is that they knew the Milwaukee Bucks would have the best player in the series in Giannis Antetokounmpo, and the Celtics had a lot of things to figure out.
When the series started, the Celtics did not look like the same team that won in the regular season. Even in the first two wins, the Celtics were playing uncharacteristically, and still figuring things out.