City went into the clash at the Etihad Stadium knowing a win would see them crowned Premier League champions, but they went down 3-2 in a first home defeat of the season in all competitions .
Pep Guardiola's side held a 2-0 half-time lead through Vincent Kompany and Ilkay Gundogan and should have scored more to cap a fine first 45 minutes, with Raheem Sterling missing two clear openings.
But United sprung a stunning comeback, with Paul Pogba scoring twice before Chris Smalling volleyed home the winner to delay City's title party.
"There's a feeling of sadness and disappointment because we played really well," he told the club's official website. "But we must turn the page as soon as possible because we have another big challenge on Tuesday.
"I could tell you many reasons why we didn't win. At the end of the day, they scored three goals and we scored two, and that's what counts. We win together and we lose together.
"If you analyse the game, we had the ball possession, we had the control, they just used the long balls and scored three goals. We played the same way we have all season, we keep the same level of performance, but today it didn't work.
2008 – Manchester City have lost a Premier League game in which they were 2+ goals ahead for the first time since October 2008 vs Liverpool (2-3). Capitulate. pic.twitter.com/Bqlr2BiHeW— OptaJoe (@OptaJoe) April 7, 2018
"We have to focus on what we did wrong and we must improve, but we mustn't forget what we did all season."
The defeat was City's second of a difficult week, following their 3-0 loss to Liverpool at Anfield, and Danilo has urged fans to get behind the team as they aim for a remarkable comeback of their own when Jurgen Klopp's men visit in three days' time.
"We need to thank them all," added the Brazilian. "They were amazing today and have been fantastic all season and they can help us so much.
"If they can repeat that against Liverpool, it will give us a huge lift and help us to overcome the result."