Isaiah Thomas showed the world that he should no longer be considered an underdog on Tuesday night when he displayed one of the best performances in the playoffs in NBA history.

Thomas scored 53 points with four rebounds and four assists during the Boston Celtics' 129-119 overtime victory against the Washington Wizards, giving his team a 2-0 led in their Eastern Conference Semifinal series.

No other player has scored this many points in the NBA playoffs since Philadelphia's Allen Iverson scored 55 points past the Hornets back in 2003. It was also the most a point guard has ever scored in a single game in the playoffs, and he became only the fifth player in team history to score 50 or more points in a playoff game.

It was quite the achievement for Thomas, all while he is still mourning the tragic death of his sister, Chyna, who sadly died two weeks ago after she was involved in a single-vehicle accident near their native Tacoma, Washington. Her funeral took place last Saturday, and the Celtics star dedicated his 53-point performance to her.

Cleveland Cavaliers star LeBron James told David Glasier of The News-Herald that he was watching the game on Tuesday night, saying: “He’s very special. A special guy. A special talent. Unique talent.

“(Yesterday) being his sister’s birthday, I believe she was looking down on him and giving him everything and more. There was no way he was going to get tired last night. I saw that watching the game. She was looking down on him and giving him extra motivation, any little touch, any little spring.”

James explained how Thomas was able to rise above the grief of losing his sister and continue to play at such a high standard at a very important time during Boston's season.

“When you’re on the court, that’s your sanctuary. That’s where you can kind of block everything no matter what you’re going through in your individual life. That’s your happy place and it definitely showed for him in his individual performance.”

These two great players could meet in the Eastern Conference Finals later on in the playoffs if Boston is able to close the series out against Washington, and if Cleveland is able to do the same to their opponents, the Toronto Raptors.