BOSTON -- Jae Crowder and Al Horford did plenty to help the Boston Celtics get the jump on the Washington Wizards in the Eastern Conference semifinals Sunday. So did Avery Bradley.

But when the series opener was over, most of the talk was about Isaiah Thomas, the physical and emotional leader of his team.

"Just been in continual amazement the last couple of weeks with his ability to function on the basketball court and excel on the basketball court," Boston coach Brad Stevens said after Thomas returned in the wee hours Sunday morning from his sister's funeral to deliver 33 points and 11 assists in the Celtics' 123-111 victory over Washington. "Today's just another chapter of that."

Thomas flew from Chicago to Tacoma, Wash., to attend the funeral of his sister, Chyna, on Saturday before flying back late Saturday night and getting in at 4 a.m. He scored 12 of his 33 points and Crowder 11 of his playoff career-high 24 (6 of 8 from 3-point range) in a 36-16 third quarter to blow it open.

Thomas, who gave an emotional speech at the funeral, lost a tooth to an Otto Porter inadvertent elbow in the first half -- the tooth flying up into the air before Thomas wound up picking it up off the floor.

Then, he helped pick up the Celtics after they spotted the Wizards the first 16 points of the game before rallying to maintain home-court advantage heading into Tuesday's Game 2.

"We always continue to just keep going," Thomas said. "We know it's not going to be I guess peaches and cream all the time. We've always played with our backs against the wall. Tonight we definitely didn't want to be down 16-0, but it happens. We locked in even more."

Thomas said he slept some on the plane and after he got home -- and then it was time for basketball. Stevens told him he didn't have to play, but you know that wasn't in question.

"It's tough, but it's the playoffs," he said. "There's no excuses. I decided to play and I just tried to give it all I got for my team, and we came out with the win."

Interviewed on ABC after the game, he said, "Basketball, when I'm on the court, it just keeps me going. I do everything for my sister now and that's all I can do."

The other side noticed.

"I think the biggest thing you can say, he's the biggest winner," Washington coach Scott Brooks said. "He's one of the biggest winners in this league. He plays with everything he has.

"I can't imagine being able to do it myself if I were in the same situation."

As far as the tooth, Thomas said, "It just bothers me to talk. My tongue goes right through my tooth ... I've always had teammates that I've always clowned them about their tooth being out, and now I'm one of them. Hopefully, we can replace it as soon as possible."

Top-seeded Boston, winning its fifth straight playoff game after losing the first two games of the first round, both at home to the Chicago Bulls, trailed 22-5 just 5 1/2 minutes into the game.

But the Celtics caught up in the second quarter, stayed close and then exploded in a 36-point third quarter to lead by 15 after three before holding off a Washington charge.

Bradley Beal led the Wizards with 27 points.

Down by 15, the Wizards scored the first nine points of the fourth quarter, but the game then belonged to Horford, who scored 10 of his 21 points in a 3:25 span to ensure the win.

Boston made 5 of 19 3-pointers (on 39 attempts) in a four-minute span late in the game -- the 19 treys matching a franchise playoff record.

Horford, who had no points or rebounds and just one assist in the first quarter, just missed a triple-double, finishing with 21 points, nine rebounds and a career playoff-high 10 assists.

Bradley added 18 points and Kelly Olynyk scored all 12 of his points in the first half off the bench to help dig his team out of the hole. Terry Rozier grabbed eight rebounds off the bench.

John Wall had 20 points and 16 assists for the Wizards. Marcin Gortat chipped in with 16 points and 13 rebounds and Otto Porter contributed 16 points and 11 boards.

Washington's Markieff Morris suffered a left ankle sprain after being fouled by Horford in the second quarter. He stayed in the game for the free throw, then left soon after, with 7:16 remaining in the second quarter and didn't return. He said after the game he will play in Game 2.

The 16-0 start was the biggest in the playoffs dating to at least 2002-03, according to STATS Inc., as the Wizards grabbed the first 12 rebounds and Boston opened 0 of 8 from the floor.

The win marked Boston's 56th straight in the playoffs when entering the fourth quarter -- dating to 1973.

NOTES: The Celtics became the eighth team in NBA history, the first in this year's postseason, to have back-to-back games with at least 15 3-pointers. ... The Wizards were missing C Ian Mahinmi (calf) ... Celtics PG Isaiah Thomas improved to 13-3 head to head against Washington PG John Wall. ... The four regular-season games between the teams (2-2) were rough affairs. Sunday was clean, except for Brandon Jennings stepping on Mike Rozier's shoe as Rozier tried to put it back on. ... Sunday marked the first playoff game between the teams in Boston since April 19, 1984. The then-Bullets had a double-digit lead after one quarter in that game and lost that one, too.