Fans fought in the street before Saturday’s New York Derby, but once the game started the hosts didn’t put up any fight whatsoever. The Red Bulls emasculated NYCFC, 7-0, in front of 37,858 fans at Yankee Stadium, handing out the most lopsided beating in their history.

“It was a disaster for us. All bad,’’ said NYCFC captain David Villa, who had been left out of Wednesday’s lineup — along with Andrea Pirlo — to focus on Saturday. It didn’t work. “We are embarrassed. [We have to] say sorry to the fans. But [after] today, we forget this game.”

That will be tough. NYCFC (4-4-5, 17 points) may well have nightmares of Red Bulls scoring on them after their rivals got a pair of goals from Dax McCarty and Bradley Wright-Phillips, a clean sheet from goalkeeper Luis Robles and goals from all three subs.

Yes, it was that kind of beating.

“It feels amazing, because the guys in this room have the right stuff. We fight for everything,’’ Red Bulls midfielder Mike Grella said. “This was a huge game. There was big pride at stake — more than even points.”

After supporters of the two teams clashed out on River Avenue under the 4 train before the game — with two arrests, made according to police — the Red Bulls showed the game has become more of a requiem than a rivalry, more of a drubbing than a derby. They have won all four meetings by an aggregate 14-2, this last one setting a club record for goals and margin of victory.

“In every aspect of the game we were second. We didn’t turn up [Saturday] and it’s never easy to concede seven goals in a derby match,’’ NYCFC coach Patrick Vieira said. “What I said to the players after the game we didn’t turn up and we didn’t play well in any aspect of the game.

“What [Saturday] was about was the emotional side of the game we didn’t control. We were a little bit too anxious, too nervous, and we didn’t play.’’

The Red Bulls (5-7-1, 16 points) sure did, and have gone 4-1-1 over their last six to climb within a point of NYCFC and two points off the Eastern Conference lead, pending Montreal’s game Saturday night.

Ronald Matarrita lost McCarty twice to allow headed goals off Sacha Kljestan corner kicks, first in the third minute and again in the 51st minute. Then Wright-Phillips padded the lead.

Grella faked NYCFC’s Federico Bravo to the ground and sent in a cross that Wright-Philips headed home. After Red Bulls supporters in the upper deck chanted “Who’s your daddy!” he followed by beating goalkeeper Josh Saunders far post with an audacious bicycle two minutes into first-half stoppage time.

McCarty made it 4-0, and all three subs scored in the second: Rookie and Lower East side native Alex Muyl, Gonzalo Veron and Gideon Baah.

NYCFC pulled Pirlo in the 75th minute for Frank Lampard to make his belated season-debut. The midfielder, making $6 million, hadn’t played a second this year due to a calf strain, and was greeted by boos.

“People were talking us up. Now is our time to take our medicine and show a bit of character and come back Saturday,’’ said Lampard, unperturbed by the reaction. “I don’t think the fans are aware of the injury I had. If I’m getting booed for being injured there’s not much I can do about that.”