It should not have been possible for Mitchell Robinson. 

A 7-footer, Robinson should not have been able to close out so quickly and ferociously on Jaylen Brown.

After Robinson stymied Jrue Holiday’s drive to the rim in the beginning of the second quarter, Holiday kicked it out to a wide-open Brown in the corner.

It appeared he’d get an uncontested 3-pointer.

Players on the Celtics bench began standing up behind him in anticipation of celebrating his shot. 

But Robinson sprinted out to Brown, who stopped his shooting motion when he saw Robinson barrelling toward him.

Robinson also stayed on his feet and hounded Brown for a few more seconds before he tipped his pass and stole it. Karl-Anthony Towns scored on the other end, and the Knicks pushed their lead to 13. 

The sequence set an early tone and was a microcosm of the relentless defensive effort by the Knicks in their 119-81 Game 6 win over the Celtics Friday night at Madison Square Garden to close out the series.

It was a complete 180 from their showing two nights prior. 

“The whole day of Game 5, it just wasn’t us,” Jalen Brunson said. “We knew that, we reflected on it and came back — we knew we needed to be ready, needed to be better. The way we prepared, the way we talked out there, the way we made an emphasis to have each other’s back and continue to cover for each other, it’s focused on the defensive side of the ball. When we’re doing that, we’re flowing.” 

The Celtics shot just 36.0 percent from the field and 29.3 percent from 3-point range.

They also committed 16 turnovers, with the Knicks scoring 22 points off them.

The Knicks also owned the glass, recording 19 more rebounds than the Celtics. 

In Game 5, defensive lapses and miscommunication — particularly in transition and on screens — resulted in countless open 3-point looks for the Celtics.

After that loss, nearly every Knicks player talked about the need to correct that very issue and how tired they were of it plaguing them.

There was comment after comment about the need to play with “urgency” and “desperation,” particularly on the defensive end. They began to sound like a broken record. 

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Then Friday night, the Knicks were hell-bent on contesting every 3-pointer they could.

Their rotations on screens were sharp. They attacked every rebound and loose ball with force. 

“We watched the film, we were discussing our communication, our effort, our sense of urgency during the game,” Josh Hart said. “That’s something that we knew we had to fix. We were able to get stops, we were able to communicate better in transition.” 

That defensive intensity and cohesion was particularly noticeable on Derrick White. After scoring 34 points on 7-for-13 shooting from deep in Game 5, White had just eight on 2-for-8 shooting from 3-point range. 

“Overall our team commitment and defensive transition, guys were covering for each other,” coach Tom Thibodeau said. “Guys were covering for each other, they were communicating really well and understood what we had to take away in order to win.” 

All season, the Knicks’ defensive regression from previous seasons under Thibodeau hovered over them. But that stifling identity returned Friday night, and brought them straight to the Eastern Conference finals.