City had registered a 3-1 win over Tottenham Hotspur at Wembley on Saturday.
United's comeback win at the Etihad only delayed City's title party by a week, and Mourinho claimed that he could "smell" the change in mood among his squad during the week.
"If I was in their position, I would be very upset if people said that Manchester City won the title because Manchester United lost to West Brom". They've got a chance to be the first Premier League team to crack 100 points and are well on their way to grabbing 100 goals in league.
But a first Premier League title, to go with the three La Liga titles he won as manager of Barcelona and the three Bundesliga titles he delivered for Bayern Munich, will be particularly satisfying.
Juan Mata echoed comments from Mourinho, accepting United were far below the required standard in defeat to West Brom. "But I expect you to be consistent", Mourinho said ahead of tomorrow's clash against last place West Bromwich Albion.
But sealing the silverware thanks to a slip from old enemies United and their boss Jose Mourinho - a long-time rival of Guardiola - was a sweet moment, especially after they lost to their neighbours in the Manchester derby last weekend. You don't win titles with inconsistency. Only in the latter stages did we come into the game with the ball.
"We were masters in complication, everything was complicated", Mourinho told Sky Sports.
City need just nine points from their final games to set a new record for most Premier League points, while another 11 goals would see them set a new goal-scoring record.
It is nearly certainly too little too late for West Brom, who look doomed to relegation.
"We didn't want or played simple, everything was slow, one more flick, trick, turn". It is a title that has been well deserved after the blues opened up a commanding lead before Christmas and, despite two league defeats, never looked like surrendering the title.
The second half was not much better but Foster did wonderfully well after 66 minutes to tip a Lukaku effort around the post before the visitors resistance was then unexpectedly rewarded with 17 minutes remaining.
A serial victor as a manager with Barcelona and Bayern, Guardiola ended his first year in England at City without silverware - his only failure to win a trophy since his managerial career started back in 2007.