"It's as loud as it gets for the playoffs," veteran JJ Redick said Sunday.
That's something that at least one Sixer acknowledged wasn't the case in the team's first-round series against the Miami Heat.
"When we were in Miami ... the gym was half-empty," Sixers reserve Ersan Ilyasova said after the team's practice. "But when you go to Boston, you will feel it. Even in the regular season, you know when you play that team, the arena is full, and they're really committed fans."
Redick, who has played in 12 postseasons, said the playoff games he played in Boston while with the Orlando Magic "were as intense of any playoff games I've played in my career."
The Sixers won both road games of their first-round series against the Heat, whose home arena is known as one of the tamer atmospheres in the league. Philadelphia will face a different challenge in Boston, where the club needs to win at least one game to advance past the No. 2 seed Celtics.
"It's always tough to play at their place," Ilyasova said. "It's always crowded, and we have to come up with a lot of energy and edge to win the game."
In addition to the raucous crowd in Boston, the young Sixers will be facing one of the NBA's top defenses in their series against the Celtics. Sixers coach Brett Brown said that one of the keys to his team's series against Boston is "just how are you going to score?"
The Celtics finished the regular season with the best defensive rating in the league. They ranked 10th among the 16 playoff teams in defensive rating entering play Sunday.
"You just go through [their rotation], they all can guard their own man. They don't need help," Brown said. "So I think the design of the team is excellent, and I think the pieces that they have, where they really are prideful in guarding their own man and they don't get into rotations much ... I think it starts with that."
Both Boston and Philadelphia have changed significantly since their last matchup on Jan. 18, but it's worth noting that the Celtics did well defending All-Star center Joel Embiid in the regular season.
Embiid shot 38 percent in three regular-season games against Boston this season; he made just one of 12 3-point attempts. Brown acknowledged that the Celtics kept Embiid "honest" during the regular season, crediting Aron Baynes and Al Horford for their defense against the center.
"They double from different spots. They leave Ben [Simmons] or T.J. [McConnell] and have random doubles," Brown said. ".... And sometimes Al will end up on Joel and just, like a smart veteran, gets underneath him and plays six inches lower and can move his feet. I think schematically, defensively they're solid."
Embiid excelled on defense in three games against the Heat but shot just 42 percent from the field and had 15 turnovers. Brown and the Sixers, who have won 20 of 21 overall, attributed some of those numbers to Embiid's lengthy absence (he missed three weeks due to an orbital fracture and concussion) and the idea that he was still getting accustomed to playing with a protective mask.
"He's rusty, so once he gets flowing, he is going to be scary," Ben Simmons said earlier this week after the Sixers closed out their series against Miami.