BOSTON — There were moments when Washington Wizards guard Isaiah Thomas clearly relished his return to TD Garden. He hugged Boston Celtics staffers, caught up with old friends and, late in the first half, smacked Marcus Smart on the rear after draining a three-pointer over his former teammate.

But afterward, as Thomas sat icing his knees following the 140-133 loss to the Celtics, the feel-good homecoming no longer mattered.

“I just want to win,” Thomas said. “We didn’t get the job done, and that was the most important thing.”

Instead of reliving the highlights of his 18-point performance, the most points he has scored since March 5, 2018, Thomas had to answer for his team’s defense. The Wizards (2-7) again folded on that end of the court, while Boston thrived beyond the three-point arc.

Washington has surrendered at least 120 points in five of its nine games. In each of those five losses, the opponent shot at least 40 percent from deep. On Wednesday, Boston’s starting backcourt of Kemba Walker and Smart, along with rookie backup Carsen Edwards, were especially lethal. Each made at least four threes, and the Celtics connected on 16 of 36 three-point attempts (44.4 percent).

“We’re just not making it as hard as possible on other teams,” Thomas said. “We’ve got to take away things that make it tough around each player that we play against.”

The Wizards’ performance wasted Bradley Beal’s 44 points on 17-for-27 shooting from field. Earlier in the day, Beal said he expected Celtics swingman Jayson Tatum to be extra motivated against the Wizards. Beal and Tatum grew up in St. Louis, attended the same high school (albeit years apart) and remain close in ways that only close friends can understand — both men bestowed the nickname of “Deuce” on sons born months apart.

If there was anyone inside TD Garden who could understand Tatum’s mind-set after he went 1 for 18 in his previous game, it would be Beal.

“He’s coming out gunning,” Beal said Wednesday morning. “I know. I know him.”

Beal wasn’t wrong. Tatum stormed through the opening quarter, making five of his first nine shots, but Beal matched his friend’s aggressiveness from the start.

Beal had made only 29.3 percent of his three-pointers and shot 40 percent overall entering the game, but he had 24 points by intermission, hitting 9 of 14 from the field, including two from beyond the arc.

Behind Beal, the Wizards stayed competitive. The teams were tied after the first quarter. Boston was up by just 68-66 at the break, and though the Celtics’ lead expanded to 16 points in the fourth, Washington pulled within 137-133 with 1:17 remaining.

The Wizards remained close despite scattered help from certain starters. While rookie Rui Hachimura scored 21 points, small forward Troy Brown Jr. was an afterthought in the offense (four shot attempts, seven points). Center Thomas Bryant contributed little in the first half (0 for 5 from the field) but recovered to finish with 14 points.

But in continuing the season trend, scoring was not the Wizards’ problem.

“We’ve got a lot of good offensive players,” Coach Scott Brooks said, “but I’ve got to do a better job of figuring out how we can get some more defenders on the floor. We’ve got to be able to be a better defensive team.”

The Wizards couldn’t match or contain Boston’s depth. The Celtics (9-1) placed all five starters in double figures, and their bench enjoyed a 40-29 scoring edge.

Thomas hasn’t started a game in Boston since he left, and Walker now reigns in his spot. Walker scored 25 points (8-for-17 shooting, including 6 for 12 from the arc) and drained the three that buried the Wizards once and for all late in the fourth quarter. But Walker wasn’t the culprit who spoiled Thomas’s return. The Wizards’ defense owns that blame.

“We’re all here to be patient,” Brooks said. “But we need to get locked in on some of these defensive coverages.”