City boss Pep Guardiola came up with a tactical masterstroke to thwart the Red Devils by playing with a 'false nine' at Old Trafford.
It saw Ole Gunnar Solskjaer's men chasing shadows in a disastrous first half – as City raced into a 3-0 lead. They eventually won 3-1.
De Bruyne said: “We did 15 minutes this morning. That's about it.
“On Monday we didn't train that way then Tuesday morning we did. But it's not like we never did it before.
“We did it already - sometimes against teams who prefer to play man against man - Cardiff, United, I think Barcelona the way we did it the first year.
“So we've done it a couple of times.
“I don't think there is a lot of difference, we played a lot of times already that way, against Arsenal.
“Obviously they tried to play man against man in the midfield so it's a little bit difficult for us because wherever we run they tried to follow us."