The Gunners went an astonishing 49 games unbeaten from May 2003 to October 2004, becoming the first and only side in Premier League history to avoid defeat throughout an entire league season.
Yet that historic run came crashing down in a heated encounter with United on 24 October 2004 – better known these days as “Pizzagate”.
Ruud van Nistelrooy’s penalty and a Wayne Rooney tap-in handed the Red Devils victory over their bitter rivals in an ill-tempered affair, with Fabregas infamously throwing a slice of pizza at Sir Alex Ferguson when tempers flared in the tunnel afterwards.
And while speaking with Rio Ferdinand on The Locker Room, Fabregas revealed Arsenal stars were left seething in the dressing room because “we didn’t feel we should have lost”.
“We were so disappointed. We were angry, we were upset,” he told Ferdinand.
“Don’t get me wrong, it had to come to an end, the Invincible, the 49 games, and it can happen at Old Trafford against a great Man United side.
“But I think it’s the way it happened. First of all, Gary Neville, what he did to Antonio Reyes, mamma mia. Every single time he had the ball.
“Wayne dived for the penalty against Sol.
“So the emotion was that we lost against a great team, which could happen, but we didn’t feel we should have lost.
“We didn’t feel it was the right time to lose our Invincible run.”
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Fabregas started his professional career at Arsenal, racking up 303 appearances for the club before leaving for Barcelona in 2011.
The Spaniard waxed lyrical about Arsene Wenger’s influence in his early days, branding him “the best coach for young players”.
“I think Arsene Wenger is the best coach for young players, definitely. I cannot see anyone better than him, because he gives opportunities, he teaches you,” he said.
“He teaches the young players how to behave and how to play the game. He has a certain ability of how to spend time with players and teach them exactly the way he wants his team to play.
“And I think in this way a lot of people talk, sometimes a young player doesn’t do well, especially now in football you don’t have patience, the press is on you, the fans are on you, they want to win.
“But he’s got that patience. You play one bad game, he will give you another opportunity. And another one after.
“Obviously at the end you will need to take it, as a young player you need to be there to take it and grab it. But he never shakes under pressure in this case and that’s not easy and he has this ability and I love the way he understands football.”