The Boston Celtics have had their fair share of unforgettable moments in the NBA. After all, they have 17 championships under their belt, and anyone would be hard-pressed to pick any one of those as their most memorable run ever. Nonetheless, there's no denying that Boston's improbable postseason run during the 2017 playoffs has to be one of their best in recent memory. This particular run was highlighted by Isaiah Thomas' 53-point gem in the second round against the Washington Wizards.

Not only did Thomas set a playoff career high in terms of scoring, but what makes this performance even more meaningful is the fact that he did this on the same day of what would have been his sister's 23rd birthday.

On April 15, 2017, Isaiah Thomas, who was then the unbridled star of the Celtics, lost his sister. Chyna Thomas passed away in a single-vehicle accident, and it was absolutely devastating for Thomas. This also happened to be on the eve of Boston's first game in the playoffs that season. Thomas flew home to Tacoma, Washington, but was able to make it back for his team's postseason opener against the eighth-seeded Chicago Bulls.

While the Celtics lost that Game 1, the 5-foot-9 point guard put forth an impressive 33 points. Boston actually lost Game 2 as well before winning the next four games to advance to the second-round matchup against John Wall and the Wizards.

May 2 would have been Chyna's 23rd birthday, and it coincided with Game 2 against Washington. Isaiah Thomas was an emotional mess, but he mustered up enough strength to take the floor. IT dedicated the game to Chyna:

“Today's my sister's birthday. She would have been 23 today,” Thomas said at that time, via Chris Forsberg oF ESPN. “So the least I can do is go out there and play for her.”

To make matters worse, Thomas had just undergone oral surgery to repair the damage of the tooth he lost in Game 1. As a matter of fact, he didn't even know if he could play hours before tipoff:

“It just wasn't a good day for me with it being my sister's birthday, me being in the hospital for three or four hours today,” said Thomas.

“I just didn't have the energy. But once I got around the guys, got to the arena, I felt like I could go. And I told [coach Brad Stevens] I could. There was no way I couldn't play on [Chyna's] birthday. I wanted to win for her. I wanted to play well for her.”

Win the Celtics did behind Isaiah Thomas' amazing 53-point performance, which he did on 18-of-33 shooting, along with five triples, four rebounds, four assists, and three steals. Simply put, that was one of the most astounding performances in NBA playoff history and was certainly Thomas' best performance ever — both from a statistical and an emotional standpoint.

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It was quite the scene:

The Celtics went on to win that series against the Wizards in an epic seven-game battle. They would, however, end up falling to LeBron James' Cleveland Cavaliers in the Eastern Conference Finals.

Still, although the Celtics fell short, Isaiah Thomas' 53-point performance will go down in history.