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".
United had denied City the chance to wrap up the title last weekend when they came from two goals down to beat their bitter rivals 3-2 at the Etihad Stadium.
City, who rebounded from the United loss and a European exit at the hands of Liverpool by beating Tottenham Hotspur 3-1 at Wembley on Saturday, have 87 points with five games left. In fact, it didn't even play a game.
United have scored a full 30 goals fewer than City this season and Mourinho has not managed to get his side to click, despite being able to bring on further talent such as Marcus Rashford, Jesse Lingard and Anthony Martial.
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The England global scored one against Spurs and won a penalty in a man-of-the-match display, but missed two glaring chances and his prowess in front of goal has always been his weakness.
By Christmas, City were already putting together 18 consecutive victories - only one short of Bayern Munich's major league record, also set under Guardiola.
"My feeling is that United will win a lot of points because they are in a good shape and have top players".
I'm buzzing, over the moon, so happy and proud to be able to share this with all of our fans, everybody who's been there to support us especially in this last week as many know it's been very hard but at the same time we've bounced back, we're champions now and thank you to all of you, It's an incredible season.
Five wins from five would give them 103 points - eclipsing Chelsea's record of 95 back in the 2004/05 season.
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"Pep's beliefs determine how his team play, the way I wanted my teams to play, so put me down as one of his admirers".
"He unlocks everything but when you think about it he did much, much better than last season and that was important".
"Playing in the Champions League at that age, sometimes it's complicated and maybe it's a good lesson for them for the future and for next season".
"You can not imagine", Guardiola said on Saturday. It's good for the Premier League as well.
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