This one-nil defeat to West Bromwich Albion was a miserable performance in its own right, made all the more galling by the fact that as a result, Manchester City have been confirmed as Premier League champions.
City are 16 points clear of second placed United, who can only take a maximum of 15 points from their remaining five games.
United prevented the Citizens from sealing the title at the Etihad Stadium last weekend after they fought back from two goals down to claim a shock 3-2 win in the 176th Manchester derby.
But that only delayed the party by one week.
But a first Premier League title, to go with the three La Liga titles he won as manager of Barcelona and the three Bundesliga titles he delivered for Bayern Munich, will be particularly satisfying. Fascinating interviews with Gary Lineker, Russell Brand, Lily Allen, Eric Cantona, Alastair Campbell, Jon Ronson, Nick Clegg and more. I was unfortunate enough to play against that quality United side that dominated in the '90s, but this side would have beaten them - that's how good they are. This was the fifth consecutive Premier League victory for Mourinho's boys and they will look forward to extend the streak against a weak side this Sunday.
The 2012 title win had the infamous last-gasp goal by Sergio Aguero. "City were the best team, sooner or later they would get the points, so no dramas when the best team wins the league", Mourinho said. Leroy Sane struck twice late on to give City their biggest win over Liverpool since 1937 and hand Jurgen Klopp's men their first defeat of the season.
Few - including Guardiola - expected it to happen on Sunday. There had been little evidence of the imperious form to follow but it was the first of a Premier League record 18-match winning run.
"We've won you the league, Manchester City, we've won you the league", sang West Brom's jubilant fans near the end of the game.
Behind United's second-half turnaround over City last weekend was a burning desire not to let their Manchester rivals humiliate them.