It didn’t happen in the MLS Cup playoffs or the Leagues Cup.

The past three U.S. Open Cup matches left them red-faced, too.

But on Wednesday, at the sixth time of asking, New York City FC finally beat the Red Bulls in an elimination game, taking a 3-1 victory in the Open Cup at Sports Illustrated Stadium to reach the last eight of the tournament.

With the Red Bulls youth movement on the other side — 18-year-old Julian Hall scored and 17-year-olds Adri Mehmeti and Matthew Dos Santos started — it was the gray-haired Maxi Moralez who unlocked the rival defense with three carbon-copy assists from the corner flag.

“I’m very happy for everybody that loves our club… [at the] end of the day, we play the game for them,” NYCFC head coach Pascal Jansen told The Post of his team’s achievement.

“So being part of this historic moment, as you mentioned, is a good thing. I hope we beat them many more times at home, but also here.”

While NYCFC are the New York club with an MLS Cup — as their fans eagerly remind opponents by belting out the word “stars” during the national anthem — the Red Bulls have historically dominated their rivals in knockout competition.

The last three Open Cup matchups between the teams had been decided by an aggregate score of 8-0 in favor of the Red Bulls, while 2023 and 2024 saw the red side of New York dump their blue neighbors out of the Leagues Cup and MLS Playoffs, respectively.

That ghastly record was quickly forgotten Wednesday, though, as Kai Trewin, Raul Gustavo and Thiago Martins each headed home goals and ultimately elicited “Who’s your daddy?” chants from the smattering of away fans in Harrison.

There were more jibes typical of a Hudson River Derby. But this time, the NYCFC fans’ hubris was rewarded.

“We are very well aware of the position we take in their lives, and it’s something I addressed going into this game, making sure that we realize what this means for our fans,” Jansen said, adding that the away support was “fantastic.”

The Red Bulls loss came despite Hall scoring his ninth goal of the season in all competitions, and on the back of a recruiting pitch to his mother from the Polish football federation’s president.

Poland, where his mother was born, didn’t qualify for this summer’s World Cup, but the uncapped, New York-born striker is also starting to hear his name mentioned as a long-shot candidate for the USA squad.

“World Cup has always been a dream of mine,” he said after Wednesday’s loss, before noting his current focus was with the Red Bulls.

Hall will likely have to wait another four years for his first World Cup shot.

His next chance to beat NYCFC, though, will come much sooner.

The sides are set for a regular-season rematch May 16.