"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". But Mourinho's team produced a stunning comeback to win the game 3-2 and put their rival's celebrations on hold.
City were without Aguero, who had suffered a rib injury in a vehicle crash, but Kevin De Bruyne made sure the Argentina striker wasn't missed as he slammed in the victor in the 67th minute.
West Brom's official Twitter account tweeted "you're welcome" to Manchester City, while its fans at Old Trafford sang: "We've won you the league, Manchester City, we've won you the league".
City are 16 points clear of second placed United, who can only take a maximum of 15 points from their remaining matches.
City's 3-1 win over Tottenham on Saturday left them on the brink of success and Manchester United's surprise 1-0 defeat at home to rock-bottom West Brom saw Pep Guardiola's side finally wrap up the title.
It is City's fifth English top-flight title, their last Premier League triumph having come in the 2013-14 season.
Manchester City's swaggering march to the title has seen Pep Guardiola's side hailed as one of the finest teams in the Premier League era.
"It's the same feeling as the first time", the 32-year-old Belgium global, who unlike his manager did watch the game, told Sky Sports. "Then the first time you lose one, you think you're never going to win another ever again". We always gave them the opportunity to be solid, compact in the low block with strong physical players.
After two relatively low-key wins in their first three matches, this stunning demolition of Liverpool served as an early sign that City were a different proposition from the team that struggled to impose themselves the previous season. I'm sure they are differences to how we play today compared to Bayern and Barcelona, we survive and live by the strength of the team.
"We conceded from a long ball, a penalty that wasn't and a set-piece - goals we can't concede". That's the reason why they were champions.
It was a far cry from his trophy-less first season with City and Kompany said Guardiola's tenacious attitude led them to the summit.
Six minutes are on the clock and each manager's current Premier League win total is below.