BOSTON — It seems nothing can stop Isaiah Thomas this postseason – be it pains big or small.

The All-Star led the Celtics to a first-round win over Chicago in a haze after learning the day before that series began that his younger sister, Chyna, had died in a car accident outside of his native Tacoma, Washington.

That pain persisted on the eve of Boston’s second-round pairing with the Washington Wizards, when he flew cross country to attend her funeral.

Then Sunday’s game brought the latest dose of adversity, when he had one of his front teeth dislodged after an early collision. But as he’s done all postseason, he continued to find a way to push through it.

Thomas had 33 points and nine assists, and the Celtics made 19 3-pointers to beat the Wizards 123-111 and take a 1-0 lead in the Eastern Conference semifinals.

“I got in at 4 a.m.,” Thomas said of his second flight to Washington in two weeks. “It’s tough, but it’s the playoffs, so there are no excuses. I decided to play and I just tried to give it all for my team.”

Thomas flew to the funeral with Boston president of basketball operations Danny Ainge and assistant coach Jerome Allen.

During player introductions, Thomas pointed to the TD Garden rafters when his name was called.

Al Horford added 21 points, 10 rebounds and nine assists. Jae Crowder finished with career playoff-high 24 points.

Game 2 is Tuesday night.

The Wizards were more energetic at the outset, jumping out to a 16-0 advantage and leading by as many as 17 points. But the Celtics rallied while Thomas was getting his tooth repositioned in the second quarter.

“I didn’t know if we’d ever score and I didn’t know if they’d ever stop scoring,” Celtics Coach Brad Stevens said.

Bradley Beal led Washington with 27 points. John Wall added 20 points and 16 assists.

Washington starter Markieff Morris played just 11 minutes before leaving with a sprained left ankle in the second quarter after landing awkwardly on Horford’s foot.

The Wizards also had a tough time responding after Stevens started Marcus Smart in place of Gerald Green in the third quarter.

“They were a little more aggressive than we were,” Beal said. “Our defense slipped a little. We lacked some IQ and focus.”

A rivalry has been simmering between the teams since last year, when Boston swept the season series.

They split their four regular-season matchups this season, but each included intense moments.

Sunday’s matchup was played at just as high a level, with a frenzied pace at times and physical play underneath the basket.

After the Wizards’ early scoring flurry, Thomas lost his tooth but initially kept playing. He found it during a timeout, but started the second quarter in the locker room. His teammates went on a 13-2 run without him to cut into Washington’s lead.

Boston led by 15 by the end of the third quarter.

TIP-INS

WIZARDS: Washington 10 of 23 from the 3-point line and shot 62 percent (16 for 26) overall in the first quarter. … The Wizards grabbed the first 12 rebounds of the game.

CELTICS: Boston didn’t score its first field goal until 6:42 remained in the first quarter, on a layup by Avery Bradley, and didn’t get its first rebound until the 5:57 mark. … Kelly Olynyk has scored in double figures in three of his last four games after doing so just twice in his first 11 career playoff games.

INJURY UPDATE

Despite what appeared to be on replays a serious sprain, Morris said afterward that it was just a normal basketball play.

“He stepped right under my foot,” Morris said of Horford. “Not sure if it was intentional or not, but that’s what happened.”

He intends to play in Game 2.

“Oh yeah,” Morris said. “It ain’t broke. That’s what I do know.”

THOMAS’ PLEDGE

In a clip of Thomas eulogizing Chyna posted by Washington NBC-affiliate King 5, Thomas was full of emotion as he expressed his pledge to live the rest of his life in her honor.

“I wanted to give up and quit and never in my life have I thought about quitting,” Thomas said. “I realized quitting isn’t an option. That’s the easy way out. I will keep going for my sister, because I know she wouldn’t want me to stop.”