Rio Ferdinand revealed Sir Alex Ferguson once destroyed Ruud van Nistelrooy after losing a Manchester Derby in November 2002.
The match did not go according to Ferguson's plans, as the Red Devils were swept aside 3-1, and Ferdinand admitted he understood exactly what the derby meant to United when he entered the dressing room following the loss.
"We got beat 3-1 at Maine Road with Shaun Goater scoring two goals," he told his Rio Ferdinand Presents FIVE YouTube channel during an interview with City legend Vincent Kompany.
"That was the first derby I played and the moment I realised how big it was was in the changing room after. We walked in and the manager shut the door. It was quiet and then all of a sudden he just erupted.
"Ruud van Nistelrooy, who was the God then, walked in with a City shirt in his hand and I remember Sir Alex Ferguson just absolutely unloaded on him. He destroyed him, saying: "If I ever see any of you walking with a City shirt ever again you'll never play for this club."
"That's how he was, he was just mad. That's when I sat there and thought: "This is a big game, isn't it?"
"I didn't realise before that game and ever since then, whether you win more or less, I knew that week leading up to a derby was all or nothing."
Kompany added the game was "everything" during his time at the Etihad. The Belgian defender said: "I lived for big games. As I child, I could be the one that didn't play well when everyone expects you to 'cause it's an easy game.
"But I never missed a big game... those games, I knew I was going to be ready. I didn't have to do much, I just focused on my preparation. The mind set changed so much over the years. The very first time I played against United it was [Carlos] Tevez, [Wayne] Rooney and [Cristiano] Ronaldo up front.
"I might as well have gone to the Trafford Centre! I'm happy I didn't have to go through that a lot in my career, that feeling was horrible.... But we won the FA Cup semi-final [in 2011] - and for us that was the tipping point. Until then we didn't really have the belief that it was a fair contest."