Sitting second to City in the Premier League, Jose Mourinho's side are now only one-point clear of third-placed Liverpool; although they do have a game in-hand on Jurgen Klopp's side.
"I have won titles, I would not be happy if someone say won title if someone lose a match", Mourinho said.
5 - City match the English top-flight record by claiming the title with five games to spare, equalling the efforts of United (1907-08 and 2000-01) and Everton (1984-85).
"I knew that sooner or later they would be (champions) and if I was in their position I would be very upset if someone said they won the title because Manchester United lost against West Brom".
It's not fair, for them.
Mourinho described United as "the masters in complicated football" and said they had been guilty of letting their 3-2 victory against Manchester City go to their heads, arguing that they would not be able to sustain a better challenge next season until Paul Pogba, among others, had started to show more consistency.
"Last not 20 years ago, it was three".
"It's incredible the way we played and I am so glad to be here and be part of this club", he said on the club's website.
A Jay Rodriguez goal in the second half was enough to separate the two sides and add a glimmer of hope to West Brom's seemingly impossible mission to avoid relegation.
"Probably because I won eight championships I was not on the moon with the victory against them because that doesn't make me feel super-happy".
United gifting City the title by losing to West Brom came just a week on from them delaying their rivals' celebrations. I know how to win and I believe in myself.
The Portuguese has suggested at regular intervals throughout the 2017-18 campaign that the Red Devils do not get the recognition they deserve.
"One of them is that we beat every team in the Premier League this season, we won against the 19 direct opponents".