The Celtics are starting to slip and need to get back to their game

At the next stop, Hauser was replaced by Jaylen Brown.

Maxey viewed Hauser guarding him one-on-one as disrespectful, and the All-Star guard should have. The Celtics could never fully recover from that storm as they lost again Wednesday, 118-114, to the six-game-under-.500 76ers.

The Celtics have been lethal in December, losing five of 11 games with a defense that plays hard when it feels like it. Not only did Maxey torch the Celtics for 33 points, Caleb Martin (remember him?) added seven 3-pointers but kept getting open.

Now the Celtics will say this was the game plan, that they will take Maxey to make tough twos, and they will give Martin, who hit just 18 3-pointers in 22 previous games this season, the open shot because he has struggled .

But there comes a time when conventional wisdom, playing the percentages and betting on the law of averages, must be discarded when the same things keep happening. Martin hit four of his seven threes in the fourth quarter when the Celtics were adamant that he would cool off.

“That was the game plan; we stick to the game plan,” Brown said. “We trusted the game plan. Martin hit seven threes and that’s tough and he’s done it before for us in the past. But going into it we felt comfortable letting him take all the shots and he hit them just down tonight.”

The 76ers have been one of the league’s bigger disappointments. Joel Embiid has missed 19 games and has barely played with Maxey and Paul George. But this was their best performance of the season, and the sleepy, borderline disrespectful Celtics were caught off guard, just like they were in Orlando on Monday when they lost to the Magic without three of their top four scorers.

The Celtics will not repeat as champions by shooting a lot of threes and playing porous defense. That’s the team they are right now.

“We’ve been inconsistent,” Mazzulla said. “This game was the inconsistency of our effort. We’re playing inconsistent basketball. We have to be better on both ends of the floor.”

The Celtics lost on a night when their starters combined for 20 3-pointers because they couldn’t get any defensive stops. They were surprised and the 76ers obliterated the scouting report by shooting far better than expected. Embiid entered shooting 21.2 percent from the 3-point line, but he made 4 of 5.

Opposing teams are no longer intimidated by the Celtics’ 3-point barrage. They carve up their defense, overwork them into 50-50 balls and cause flurries of turnovers. The Celtics started Christmas Day like they had too much eggnog, committing six turnovers in the first quarter in a game they were never in control of.

“We just came out too casual,” Brown said. “I think we went to our spots. Nobody was sprinting down the floor, just hanging around, just trying to swing back to get the ball instead of just pushing it down the court and just being aggressive. We just couldn’t put the whole 48 (minutes) together. I’m not really sure why. As a group, we have to be better.”

Jayson Tatum has enjoyed his share of best-on-the-floor moments carrying the Celtics as they overwhelm opponents with their accurate 3-point shooting and cohesive defense. And he realizes the Celtics have lost their swagger a bit.

They have more home losses (five) than they had all of last season (four). Opponents are better prepared, using different game plans and destroying Boston’s poor interior defense. The Celtics respond by taking threes and making valiant rallies in late games that fall short.

“We’ve always hung our hat on being a really, really good defensive team that takes pride on that end of the ball, and we’ve got to get back to that,” Tatum said. “We have to take some ownership, recognize that the things we’ve done are not that good. We have to look in the mirror and man up. We fully believe in ourselves, the things we can do when we’re completely locked up. We’ve done it time and time again. We’ve just had some outages recently.”

Before the season, Mazzulla promised that his team would not see this season as a chance to repeat, but a chance to chase the same goal as the other 29 teams. They wanted to disregard the championship in 2024 and play with the same passion and determination as last season, when they were simply challenging.

But after the first six weeks of the season, the Celtics have softened. They don’t play with the same intensity. They lost their confidence. They are sloppy with the ball, hit threes, lack defensive assignments and rattle free throws. And the rest of the league is enjoying their slide.

“We’ve been to three straight conference finals, two finals the last three years,” Tatum said. “We’ve had everybody’s best shot over the last three years, so it’s not something that should catch us off guard or anything like that. It should be something that’s expected. I keep saying that.” We’ve got to get back to ourselves, our identity.” We haven’t shown that the last couple of games or so and we’ve got to lock in again.”

Gary Washburn is a Globe columnist. He can be reached at [email protected]. Follow him @GwashburnGlobe.