Isaiah Thomas had just finished off one of the most spectacular individual performances in recent NBA playoff history — 53 points on 33 shots in 45 minutes, 29 of ’em coming after the end of the third quarter. After leading the Boston Celtics to a 129-119 overtime win over the Washington Wizards in Game 2 of their best-of-seven Eastern Conference semifinals series, TNT sideline reporter David Aldridge had just one question for the All-Star point guard: “Where is this coming from, man?”

Thomas offered a simple, and touching, answer.

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“It’s my sister,” Thomas replied. “It’s her birthday today. Happy birthday. She would have been 23 today. Everything I do is for her. And she’s watching over me. So that’s all her.”

Chyna J. Thomas died in a one-car crash on Interstate 5 in Tacoma, Wash., at around 5 a.m. on Saturday, April 15. According to the Washington State Patrol, she was not wearing a seatbelt, and she died at the scene of the crash.

She was just 18 days shy of her 23rd birthday, which she was planning to spend with her brother in Boston, where, she hoped, he’d still be plying his trade in the playoffs. Instead, Thomas had to fly back to Tacoma last weekend after the Celtics eliminated the Chicago Bulls to deliver the eulogy for his little sister.

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

Thomas then returned to Boston for Game 1 against the Wizards, scoring a team-high 33 points with nine assists to help stake the Celtics to a 1-0 series lead. For an encore, he authored the second-highest-scoring game in the postseason history of one of the NBA’s most decorated franchises.

Later in the interview, Aldridge asked Thomas where he’s finding the strength not only to play in the days after his sister’s death, but to excel in the crucible of the postseason.

“My family. My friends,” Thomas replied. “They tell me to just keep going. My sister wouldn’t want me to stop. The only thing about it is, once I leave this gym, I hit reality, and she’s not here. So that’s the tough part. But when I’m in this arena, I can lock in, and I know everything I do is for her.”

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Dan Devine is an editor for Ball Don’t Lie on Yahoo Sports. Have a tip? Email him at devine@yahoo-inc.com or follow him on Twitter!

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