Two goals from former United forward Carlos Tevez proved enough for Manchester City to claim a narrow advantage going into tonight's return leg.
Related ArticlesZoran Tosic joins Cologne on loanMancini: Manchester must not look back in angerPolice arrest three more ahead of Carling Cup semiNemanja Vidic on course for RealMan Utd v Man City: match previewFerdinand to miss Manchester derbyBut despite the frenzied build-up to the game, and escalating rivalry between the two clubs, United midfielder Giggs insists that the Old Trafford club must look at the bigger picture.
He said: "Of course, it's a derby, but it's also a cup semi-final with a place at Wembley at stake and a trophy at the end of it. We're the holders and we want to defend our trophy.
"It was a great game at Eastlands last week and, although we didn't get the result we wanted, if we perform like that again at Old Trafford, then we should be okay.
"The supporters are going to play a massive part. It was a great atmosphere at Eastlands and our fans were absolutely brilliant. We need them to get behind us again because it really does make a difference.
"It's not often you play City in a night game. It'll be like a European match in some respects, which is obviously something we're used to and something which we usually thrive on.'
United are likely to go into the game without Rio Ferdinand, who is expected to plead guilty to an FA charge of violent conduct before 6pm today.
Ferdinand, charged as a result of a clash with Hull City's Craig Fagan on Saturday, will receive a three-match ban, which would commence today, if he accepts the charge.
Despite Ferdinand's anticipated absence, United manager Sir Alex Ferguson is keen to field a strong team against Roberto Mancini's team.
He said: 'We are trying to get some continuity with our team selection now. I think that is important because we have had a topsy-turvy spell of defenders being injured or out all season.
'Getting those players back and having a continuity of defenders will be important to us. That's the key for us.'
Meanwhile, United defender John O'Shea is hopeful of playing again this season, despite being ruled out for the campaign by Ferguson last week as a result of a thigh injury.
O'Shea said: "The boss said that I could be out for the rest of this season, but 'could' and 'would' are two very different words.
"To be honest, I am much more hopeful about my injury situation. I am improving at a very steady pace and I am very hopeful of being back in the action sometime in March."