The Italian manager also praises Mario Balotelli for remaining 'serious on the pitch' after the striker lit the fuse in record breaking victory
The Italian said that the scoreline was not the most important factor on the day but the win that takes them five points clear of their Manchester rivals.
"I think that after the sending off it was easier but we were playing very well. For the first 25 minutes United played well but they didn’t have more chances," he told Sky Sports.
"It’s good but I think that it’s not important 6-1 [the scoreline], it’s important that we beat a fantastic team.
"This is normal when you play at Old Trafford because United are a strong team."
The former Inter coach also praised the performance of Mario Balotelli after the striker scored twice and made the break which forced United defender Jonny Evans into a game-changing red card foul. However, the Italian refused to be drawn on what the win could mean for City's title challenge but praised their opponents for their attacking spirit throughout.
"I am happy for him because he scored two important goals, because he played well because he was serious on the pitch," he continued.
"I’ll tell you in three or four weeks [about the title race] but I think it is important for our confidence because it isn’t easy to come here and beat United.
"I have more respect for United now because after the sending off they continued to play to try and score I think this is an incredible mentality.
"If we want to improve and to arrive at the top like them, we should improve in this mentality.
"It’s an important three points because we have one game less and we played here. I don’t think there will be many teams that come here to win."