BOSTON – Celtics star Isaiah Thomas stood at a dais in Tacoma, Washington, on Saturday afternoon, black sunglasses on to shield the tears he was fighting back. He was clutching an iPhone to ensure his words came out correctly as he said goodbye to his sister.

"When I found out the news, I wanted to give up and quit. Never in my life have I thought about quitting," Thomas told the family and friends who gathered to celebrate the life of Chyna Thomas, who died April 15 after a single-vehicle accident.

"I realized quitting isn’t an option," added Thomas. "That’s the easy way out. I will keep going for my sister because I know she wouldn’t want me to stop. I love you, Chyna, and I miss you so much, and everything I do for the rest of my life will be for you."

Before Thomas left the Celtics in Chicago after Boston's Game 6 triumph on Friday that sealed a first-round victory over the Bulls, Celtics coach Brad Stevens reminded his star guard that, if the events of Saturday were too overwhelming, he didn't have to rush back for Game 1 of an Eastern Conference semifinal series against the Washington Wizards.

But there was Thomas, a bit bleary-eyed after a cross-country flight that didn't arrive in Boston until 4 a.m. ET, on the court at TD Garden to prep for the team's pregame shootaround at 10 a.m.

Thomas scored a game-high 33 points on 11-of-23 shooting and added nine assists in 38 minutes as the Celtics rallied for a 123-111 win over the Wizards. Boston leads the best-of-seven series 1-0; Game 2 is Tuesday night.

"Basketball, when I'm on the court, it just keeps me going," Thomas said during an on-court interview after the game. "I do everything for my sister now. That’s all I can do."

Coaches and teammates have run out of words to properly describe exactly what Thomas is doing this postseason. Thomas learned about his sister's death on the eve of the playoffs, little more than 24 hours before Boston opened its first-round series against the Bulls.

Despite being overwhelmed with grief, he stayed with the team and played in Games 1 and 2, both losses. During a two-day break in the schedule, Thomas made his first dash home to Tacoma to be with loved ones. He returned with a bit more zest, and his performance in Game 3 might have saved Boston's season.

With only 38 hours separating the end of Boston's series against Chicago and the 1 p.m. tipoff for Game 1 on Sunday against the Wizards, Thomas dashed to Tacoma again to bid farewell to his sister and then made the long flight home. That's roughly 4,200 miles in the air in little more than 24 hours.

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

Celtics center Al Horford called it "unreal." Stevens called it "unfathomable." Both admitted they are not certain they could endure what Thomas has gone through and still perform the way he has in these playoffs.

"It was unreal. Everything that was going on for him off the court, and for him to still be able to function at this level, [it is] just strong character. His will is very impressive," said Horford. "I don’t know if I would have been able to handle it in that way. He’s able to come in here and say 'no excuses,' but he has a perfectly good excuse. He still comes out, he’s focused ... it’s a credit to him and his way to get prepared for the game."

Echoed Celtics guard Avery Bradley: "It’s incredible. For him, despite everything he’s been through, to be able to come here and work at a high level, it’s incredible."

Before Sunday's game, Stevens noted that he had been texting Thomas on Saturday. Thomas had implored his coach and teammates to begin preparation for Sunday's game and pledged to do the same during his downtime.

Stevens said that when he talked with Thomas, he steered the conversation away from basketball.

“I saw the [video] clip of [Thomas] speaking [Saturday] at the funeral," Stevens said. “We were texting [Saturday], and obviously I’ve had a lot of talks with him over the last two weeks. My discussion with him wasn’t about basketball. It was just about how hard it is to speak at a funeral.

“He’s been through a lot. And he just continues to amaze us all when he steps on that court with his resolve and his ability to just kinda be, as he’s called it, his sanctuary. He’ll continue to have really tough days; I don’t think that’s going to stop."

A bit of levity arrived midway through the first quarter of Sunday's game when one of Thomas' front teeth got knocked out as he defended Wizards forward Otto Porter. Given all that Thomas has endured, Thomas couldn't help but smile as teammates laughed at the sight of his toothless, blood-covered grin.

Maybe it helped relax Thomas, because Boston, down 17 when Porter made a jumper right after the unexpected tooth extraction, rallied to make it a game with help from Thomas' offensive explosion. A dominant third quarter pushed Boston ahead by double digits, and the Celtics held on from there.

Thomas got help from his teammates. Kelly Olynyk helped Boston rally out of a big hole in the first quarter; Jae Crowder scored a postseason career-high 24 points and finished plus-26 in 35 minutes of floor time; and Horford was one rebound shy of a triple-double (21 points, 10 assists, 9 rebounds).

But this day belonged to Thomas, given all that he endured to simply be on the court.

“I’ve said it before: I’ve 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," said Stevens. "And today's, like, just another chapter of that. Just amazed.

"I think I’ve used the word unfathomable, and I’d stick with that. I can't imagine being able to do it myself, if I were in the same situation, and it's incredible. He’s incredible."