Paul Pierce loses control of the ball in front of John Wall. (Michael Dwyer/Associated Press)

Nene had been experiencing discomfort in his back for a few days, but when he woke up in his hotel room on Sunday morning, the Brazilian big man said his back had “shut down.” He tried some physical therapy, had a massage, and worked on the training table about 90 minutes before the Washington Wizards were set to play the Boston Celtics at TD Garden.

Shortly before tip-off, Nene informed Coach Randy Wittman that he wouldn’t be able to go, leaving the Wizards without one of their most important pieces against a team that they have had no success with this season. To say that the Wizards were defeated before they started wouldn’t be totally accurate, but it wasn’t long after the game began that they were well on their way toward an 88-76 defeat.

After blowing huge double-digit leads before losing to playoff contenders in their previous two games to Indiana and Atlanta, the Wizards (11-37) took a different approach against Boston: Instead of waiting until the fourth quarter for an inexplicable collapse, they basically conceded defeat early, with poor shooting and a disorderly defense creating such a large deficit that they were unable to overcome the experienced Celtics.

“That’s not who we’ve been for a long time,” Wittman said. “There was no fight in the first five minutes of that game. That was a layup drill with no defense. I don’t know why it happened.”

Already short-handed without Nene, the Wizards didn’t have Trevor Booker in the fourth quarter as he dealt with foot problems and a sore right knee. Jordan Crawford led the Wizards with 20 points, but the team shot just 34.5 percent from the floor and lacked sufficient firepower to overcome a 25-point first-half deficit.

Kevin Seraphin got his fifth start of the season and responded with career-high 15 points and 11 rebounds but wasn’t seeking any congratulatory pats on the back afterward. “It doesn’t mean nothing. I had my career high but we lost the game,” said Seraphin, who found out that he was going to start about 30 minutes before the game. “That’s a good team. Once they put us down 20, that’s difficult to come back from.”

John Wall finished with 12 points and nine assists, but he missed 12 of his 17 shots and also collected a technical foul in the fourth quarter as the game unraveled after the Wizards made another futile run. Rookie Jan Vesely had a career-high 11 points and six rebounds and Chris Singleton also had 11 points for Washington, which has lost three in a row.

The Wizards were in a noticeable funk at the start, with Booker claiming there may have been a “hangover” from the loss to Atlanta the night before. They missed their first eight shots and didn’t connect on a field goal until Booker made a jumper from the top of the key with 7 minutes 19 seconds remaining in the first period — that brought his team with 15-4. Booker has been playing with plantar fasciitis in his left foot for the past few games but he twisted his right ankle after grabbing an offensive rebound then twisted his right knee shortly thereafter when he drove down the lane and missed a dunk.

“I’m all right,” Booker said after the game. “I knew we were short-handed already, but I didn’t want to leave the guys empty-handed.”

Ray Allen sat out the game with a sore right ankle, but Avery Bradley made sure the Celtics didn’t have any sort of letdown as he went 7 for 7 and scored 15 of his career-high 23 points in the first quarter. He outscored the Wizards in the first period, as they set a new season low with just 12 points and shot just 3 for 22 (13.6 percent).

“I could have scored those layups,” Wittman said. “I am being serious. We didn’t have anybody guarding him. He ought to send us a postcard of thank-yous or something for allowing him to score.”

Bradley made a long jumper to give the Celtics a 55-34 lead to start the third quarter, but Wall helped the Wizards go on a 13-0 run to get back into the game. He hit a pull-up jumper, made a driving dunk down the lane, then buried another jumper. Crawford then sandwiched a three-point play and a difficult fadeaway around a Seraphin layup to bring the Wizards within 55-47. But within two minutes, they were back down by 18.

Paul Pierce added 21 points and eight rebounds and Rajon Rondo had 11 assists and four points for the Celtics (26-22), who swept the four-game season series with Washington.

The Wizards will complete their first set of three games in three nights on Monday against Detroit at Verizon Center. Wall said the Wizards have to come out ready to play against the Pistons and “act like it’s a playoff game for us. Act like it’s a game we need to win. And stop the bleeding, losing three in a row. Get one at home.”

Nene wasn’t sure if he would be available against Detroit and said he would take a “day-by-day” approach with his back. “Let’s see how I feel, how I wake up. You know, back is a little different. If you don’t feel good, solid to do your movement, that can be worse. So we just try to prevent it a little bit.”