The Celtics repeatedly have shown they can play pretty basketball and flourish in that style. They have looked unbeatable in stretches this season, such as the opening quarter last week in Chicago, the third quarter in the opener against Philadelphia, and the third quarter at Miami.
Yet, when shots aren’t falling and the offense becomes rugged, this edition of the Celtics had yet to show they can win with defense.
The Washington Wizards presented an opportunity to display Boston’s renewed defensive emphasis. And it also gave the Celtics a chance to hold a double-digit lead when the offense stagnated Sunday at TD Garden.
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The first quarter was beautiful, and that offensive prowess spilled into the second period. The final 30 minutes weren’t as picturesque but just as effective because of the defensive resistance in a 112-94 win.
The Wizards shot 38.8 percent from the field and missed 25 of 32 3-pointers. Most importantly, the Celtics forced the Wizards to compete without the offensive contributions of prolific scorer Bradley Beal, who went for 31 points in Friday’s loss to the Indiana Pacers.
Beal did not score until the 2-minute, 29-second mark of the third quarter and finished with 12 points, none of them meaningful. This came two nights after the Cavaliers’ Donovan Mitchell and Caris LeVert went thunder and lightning on the Celtics with 41 points each. They got anything they wanted that night.
Beal struggled to get off a clean shot, and looked uncomfortable when he did.
This is how the Celtics won so many games last season, with defense. Sunday, they held their first opponent under 100 points. They were more aggressive in their defensive switching and appeared more comfortable with coach Joe Mazzulla’s stressed concepts.
The Celtics spent Saturday’s practice emphasizing defense after Friday’s debacle. Of course, there are going to be nights when they win because of their offensive prowess, when Jayson Tatum and Jaylen Brown are tallying 30 points each. But on Sunday, they didn’t need that much production.
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They combined for 8 of the Celtics’ 54 second-half points and each played just 1:40 of the fourth quarter.
“I saw the same effort that we had in the first [five] games, I saw a commitment to the details and a commitment to the execution,” Mazzulla said. “Guys are always going to play hard. We just have to continue to execute and be detailed and as [consistent] as we were tonight.”
Sunday was an encouraging sign that these Celtics eventually will become an above-average defensive team. They have the personnel. Malcolm Brogdon and Marcus Smart can be terrors in the backcourt. Tatum was partly responsible for holding Beal scoreless until late in the third quarter. And despite the absence of Robert Williams, the Celtics have solid defenders in the paint.
Mazzulla obviously is beginning to favor Luke Kornet as the primary backup to Al Horford after an experiment with the foul-plagued Noah Vonleh. And while Kornet provides little threat offensively — he passed up on a number of chances to score at the rim in a Ben Simmons-like fashion — he does offer defensive resistance.
The Celtics are going to need Williams back to become an elite defense, but they have enough defenders to prevent what happened Friday from happening again.
“We’ll have a really great quarter and then we’ll have a letdown, 30-plus points in a quarter,” Brogdon said of the defense. “It’s really about putting those spurts together and being connected and playing defense for 48 minutes.”
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The Celtics need their share of easy nights. They understandably tussled with Philadelphia and Miami in their first two games before pulling away. Their defense was nonexistent against the Orlando Magic until the final six minutes, when they capitalized on a young team that didn’t know how to close out games.
Against Chicago and Cleveland, there were considerable dropoffs, reminiscent of early last season when the Celtics gave away so many games with fourth-quarter collapses. This current bunch is good enough and should be experienced enough to comprehend the importance of putting an inferior opponent away early with effort on offense and defense.
“In previous games we started hot like we did [Sunday], especially in the Chicago game and we kind of let up,” Smart said. “Tonight our sole focus was we’re going to have hot starts like that, offensively and defensively, and sustaining it is our problem. We wanted to come out here and make a big emphasis on it and once we did, not to let it slow down or take our foot off the gas pedal.”
Mazzulla’s comment Friday that the Celtics have to learn how to win again is only partly accurate. They should have enough experience and evidence from last season to understand that every opponent should be taken seriously and good offense does not necessarily relate to good defense.
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Boston took a 51-27 lead midway through the second period and then began rushing possessions, seeking knockout 3-pointers, and slipping on defense, allowing the Wizards to slice the deficit to 11 by halftime. The Celtics responded by restoring order in the third period, playing better defense, and taking care of the ball to extend the lead.
This early season is about applying those lessons learned from last season and ensuring the Celtics don’t give away games because of apathy or overconfidence. Sunday was a positive response after consecutive losses. The next step is eliminating those mental lapses altogether.
Gary Washburn is a Globe columnist. He can be reached at gary.washburn@globe.com. Follow him @GwashburnGlobe.