Kevin De Bruyne says Manchester City spent just 15 minutes preparing the false-nine tactics that helped to blow Manchester United away in the first half of Tuesday's Carabao Cup tie.
City blitzed their rivals in the first-half, going 3-0 up in 38 minutes during the semi-final first leg at Old Trafford.
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Marcus Rashford pulled a goal back for United after half-time but they went down 3-1, with Bernardo Silva playing a key role in his unfamiliar false nine position.
He scored the opener with a brilliant long-range strike and also had a role in the other two goals while strikers Sergio Aguero and Gabriel Jesus started the game on the bench.
Pep Guardiola often used a false nine when he was in charge at Barcelona but has rarely done so at City.
But despite their lack of experience with the tactic, De Bruyne said: "We did 15 minutes on it in the morning, that's about it.
"We didn't train that but it's not like we never did it before - we did it sometimes against teams that prefer to play man-against-man; Cardiff, United, in Barcelona away we did it the first year with Pep, so we've done it a couple of times.
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"With Bernardo dropping it is four against three in the midfield, so they have to choose what they do - if they put their defender up there is more space behind and if not Bernardo is going to be free and that is what we tried to do.
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"I think overall we played well. The second half they tried to put a bit more pressure on us and we made one mistake and they scored from it.
"I don't think they had a lot of chances and I think we should have scored more but in the end 3-1 is a good advantage. We know it is not over but obviously it was a good game for us."
'A 3-1 home defeat to rivals Manchester City might not sound so emphatic but the reality was rather different. Pep Guardiola had won on his three previous visits to Old Trafford in the Premier League but never like this. United conceded three goals in the first half for the first time here in 22 years. The gulf between the two teams was obvious to everyone.'
Who were the star performers as Manchester City defeated Manchester United 3-1 at Old Trafford in the Carabao Cup semi-final first leg...
Manchester City are aiming for a third successive Carabao Cup title win and have put themselves in pole position, but, despite the positive result, boss Pep Guardiola is adamant that the semi-final is still in the balance.
He said: "In the first minutes, it was tight, they had one or two counter-attacks and the second shot. It was an outstanding goal from Bernardo and since then we played really good with a lot of passes arriving from behind.
"In the second half, they changed the shape from a diamond to a 4-4-2 and we struggled a little bit, but it's a good result.
"It's not over though, it's Man United and we see how they can come back... but hopefully with our fans, we can make a good game and reach the final again."