's historic bid for five trophies this season by beating Sir Alex Ferguson's team this week and going on to win the Champions League with Inter Milan.
The self-proclaimed Special One returns to take on an English team for the first time since his dramatic sacking from Chelsea in September 2007, with Inter hosting United in the first leg of their Champions League tie at the San Siro Stadium in Milan on Tuesday.
And Mourinho, whose team beat Bologna 2-1 yesterday afternoon, promised to outwit his old adversary in the most glamorous match in world football so far this year.
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Inter, clear at the top of Serie A and chasing their own treble, take on world club champions United, who are eight points clear in the Premier League and face Tottenham in the Carling Cup final next weekend, followed by an FA Cup fifth-round tie.
Mourinho said: 'Sunday morning will be the first time I am going to speak to the players about the game and I will start by saying, "We can do it, we can beat them". But the point is not just to beat Manchester United.
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For me, you either win the Champions League or you don't win it. If we beat United and lose the quarter-final, what is the point?
'The game against United will only be important if we go on to win the Champions League. Otherwise it is irrelevant.'
If Mourinho was in danger of sounding unimpressed by the prospect of facing United, he was quick to take the opportunity to praise Ferguson's team in the run-up to the match, dismissing the claims of Liverpool manager Rafa Benitez that fixture schedules and the intimidation of referees were key reasons for United's dominance.
'There is no bias,' said Mourinho. 'Chelsea were champions because we were the best team and Manchester United are champions because they are the best team. If Liverpool want to win, they have to be better.
The best team wins.' And in explaining why he did not rest key players at Bologna yesterday, Mourinho delivered another thinly-veiled attack on Benitez and Liverpool.
'We do not rest players as we have to win the title. The big clubs are the ones fighting for the title and the Champions League at the same time.
'Before we played Liverpool in the Champions League semi-final in 2007, Liverpool rested ten players against Fulham. Liverpool lost and that result helped Fulham against another club in the fight against relegation.
'We're playing to win the title, so there's no rotation.'