But the Baggies had other ideas as they frustrated the Red Devils and snatched the victor through Jay Rodriguez with just over 15 minutes to go.
The 2016-17 Blues vintage only failed to take three points on nine occasions, but it appears something of a formality that Guardiola's men will break the record as their remaining games are against Swansea City, West Ham, Huddersfield Town, Brighton & Hove Albion and Southampton.
Something tells us City will get there.
Mourinho claimed afterwards that he had not been happy after the City result because he knew they would win the league regardless and he accused some of his players of getting carried away.
Spurs dominated the proceedings during United's previous visit to Wembley in the Premier League, and though the fixture is considered a neutral venue this time around, their rivals should have the ascendancy with the better feel of the surroundings.
The Baggies official Twitter account tweeted a graphic on the full time whistle showing the score accompanied by a photograph of Jay Rodriguez celebrating his goal.
Victory for West Brom came in just the second game for caretaker boss Darren Moore and the 43-year-old believes restoring a sense of togetherness is the key to ending a torrid season on a high. They are unbeaten in their last four versus Bournemouth (3-1-0) since a 2-1 loss at Dean Court in the first Premier League match between the teams in 2015.More news: Allegiant Air Had More Than 100 Big Problems in 2 Years
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But you wouldn't have guessed it with the way Mourinho set his side out on Sunday afternoon, at Old Trafford no less.
Mourinho has been publicly critical of Pogba on a number of occasions this season.
It is nearly certainly too little too late for West Brom, who look doomed to relegation.
The English goalkeeper, who recently turned 35, averaged 2.19 saves per game before the match against his former club and pulled off another hat-trick of saves to deny United on Sunday.
The first half was a awful advert for the English top-flight.
From an attacking perspective, too, the Red Devils looked to be running out of ideas, even if Ben Foster needed to be at his best to deny a Lukaku header. "Eight titles are eight titles and three Premier Leagues are three Premier Leagues", he said.
And despite a torrid week when he had to lose three straight games, two in the UEFA Champions League and one in the league, Guardiola, 47, can heave a sigh of relief knowing he already has two trophies in the bag after the Carabao Cup success against Arsenal earlier in the year.