The Manchester United boss welcomed the Red Devils' bitter rivals to Old Trafford for the big game of the day in the Premier League.
He spoke earlier in the week about how he would need everyone at the club to up their game - including the fans - for this weekend's monster clash.
And he's revealed what he said to his players prior to kick off.
Mourinho told Sky Sports: "How do we win today? I would say to my guys, 'don't lose the identity that we have built up during the last couple of months'.
"And that DNA was more solid because of the happiness of the results.
"This is something we cannot lose.
"This is our way of playing football.
"We have to play in the same way because it is something we want to develop."
