The Red Devils came into the fixture in high spirits, having beaten neighbours and champions-elect Manchester City 3-2 last week.
And his reaction after Manchester United handed the title to City on Sunday after a shock 0-1 defeat against West Brom at Old Trafford was no different.
United was second-best all afternoon and Darren Moore's men earned its reward for a spirited display thanks to Jay Rodriguez's close-range header 17 minutes from time.
City have won the title with five games to spare, equalling the English top-flight record which was first set by United in 1907-08.
"I don't know if I was the first or second or third but I congratulate them face to face when I had the chance", said Mourinho.
The Blues could have made history though and taken the title sooner if they hadn't lost 3-2 against Manchester United at the Etihad Stadium. "Probably because I won eight championships I was not over the moon with the victory against them (City) because that doesn't make me feel super happy".
United's afternoon was symptomatic of their entire season.
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Jose Mourinho all but conceded the title after the first Manchester derby with five months of the season remaining as City moved 11 points clear at the top of the table.
Mourinho is quoted as saying by Sky Sports: "We are not going to spend more than we can".
Mourinho said the there was no continuity or fluidity in the team's play on Sunday, but he said he thought the result was harsh.
City tied the record for earliest date of sealing the Premier League title, sharing the mark with the 2001 United squad. "I know how to win, I believe in myself but I don't play", added the former Chelsea and Real Madrid manager. You don't win titles with inconsistency.
But Raheem Sterling scrambled in a 97th-minute victor, and although the England forward was sent off in the celebrations that followed, it proved to be a launchpad for a special season for both Sterling and City.
The first half was a bad advert for the English top-flight. The England midfielder's effort lacked venom, though, and was parried to safety by David de Gea. Arsenal are second on 17,520, reported Opta.
England worldwide Rodriguez scored his 11th goal of the season when the home side failed to clear Chris Brunt's corner.