The Knicks had their X’s and O’s in order Thursday night.

The same can’t exactly be said of one of their fans.

During a stoppage of the Knicks’ Game 5 win over the Pacers at the Garden on Thursday, a pair of fans went head-to-head in a full-court game of tic-tac-toe.

Make a basket, get a letter and use it to beat your opponent in one of the first games we all learn as children.

One of them, however, forgot to defend, eschewing a block between a pair of Xs to drop an O in an opposite corner, paving the way for a disastrous loss.

The blunder was costly enough — the fan didn’t win the $1,000 prize — and doing so in front of 19,812 fans at the World’s Most Famous Arena, a set that included a stacked celebrity row of Timothée Chalamet, Kylie Jenner, Ben Stiller, Mariska Hargitay and more.

Let’s hope the fan didn’t try to ease their loss by watching “SportsCenter” when they got home, either, as host Scott Van Pelt nearly lost his mind trying to figure out what happened.

“What are we doing? This… This… Have you ever played the game?” he decried during the midnight showing on ESPN.

“There’s an X here and an X here … the O has to go here. It isn’t complicated. It’s a simple game. We play it as children.”

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Van Pelt didn’t stop there, as the breakdown continued.

“I get it: you’re running, there’s a lot of people watching,” he said. “Really, the second O is a catastrophe. How the hell do you put it there when the X is here? Now you understand, I’ve got to block the two Xs. … What are we doing? I understand. Timothee Chalamet, he’s in the front row … you’re nervous.”

The Knicks — unlike this fan — get another crack at their foe in Saturday’s Game 6, thanks to the 111-94 win Thursday night.