Philadelphia is 23-6 at home this season.
Despite the electrifying, new-look offense, all of coach Brett Brown's attention is on defense and preparing for the playoffs.
"All I think about is, 'How do you have a defense that can play in the playoffs?'" he said.
"Right now, the pace of the game made the game a little bit difficult. I think our defense right now is a B- or C+. We're OK. We turn it up; we turn it down. It needs to be better than it is. It's certainly going to have to be better against the Celtics. But the notion of what's the end game, it's always about the playoffs."
Harris scored 22 points on Sunday, and JJ Redick added 21 for the Sixers. Redick has scored in double figures in 61 consecutive games.
Harris is already meshing quite nicely with his new team.
"Every new situation, you just want to come in and kind of play off the love of the game and let everything else flow from there," Harris said. "I've been able to get better year after year to be able to understand the game, understand my spots on the floor, understand how I can help a team."
The struggling Celtics have blown big leads in losing their last two games. After building an 18-point lead and losing to the Lakers on Rajon Rondo's buzzer-beater, the Celtics then gave back a whopping 28-point advantage and fell to the Clippers, 123-112 on Saturday.
Gordon Hayward scored 19 points while Jayson Tatum and Terry Rozier added 16 apiece. To make matters worse, Irving left with a strained right knee in the second quarter. Boston on Monday listed Irving as out against the Sixers.
"I guess it just kind of snowballs on you," Hayward told reporters. "It's the NBA man, it's how it works."
Last season, Irving suffered a left knee injury that kept him out for the final 15 regular-season games and all of the playoffs. Irving had 14 points in 14 minutes on Saturday before going down.
Following the loss, Celtics forward Marcus Morris had some strong comments.
"I don't see the joy in the game," Morris told reporters.
"I watch all these other teams around the league and guys are up on the bench, they're jumping on the court, they're doing all of this other stuff that looks like they're enjoying their teammates' success. They're enjoying everything and they're playing together and they're playing to win.
"And when I look at us I just see a bunch of individuals."
--Field Level Media