After losing the Premier League title in the final seconds of last season to their bitter local rivals, Sir Alex Ferguson was on a mission to bring the trophy back to Old Trafford and restore the balance of power in Manchester.
Having successfully done so, in exceptionally efficient style, with Player of the Year Robin van Persie added to an already very strong squad, some fans can't help but wonder what could have been.
Rewind to February 14 and United had just been to the Bernabeu and drawn to a Mourinho and Ronaldo led Real Madrid side, coming away in the stronger position after Danny Welbeck's away goal.
The feeling across the country was the Old Trafford side had a real chance of winning the tie and perhaps going on to win the tournament. Coming back to present day and they've have recaptured the title from City, but can only watch as the brilliant German top two crush the Spanish giants Madrid and Barcelona. So where did it all go wrong?
Answer? The referee. United were deservedly 1-0 up (without the benched Wayne Rooney), after dominating for much of the first hour at Old Trafford, until Nani challenges Alvaro Arbeloa for a high ball.
So a free kick and possibly a yellow-card surely? No, the stadium falls silent with shock as the referee dismisses Nani, leaving United with ten men and knocking the momentum from under them.
Mourinho, sensing his chance to capitalise brings on Luka Modric who does just that, scoring a fine goal. As fate would have it, former hero Ronaldo gets the decisive goal and knocks Sir Alex's men out of the competition.
You could argue that their best performances during the season came against Real Madrid both away and for the first hour at home, and yet football is a funny old game and this became the most disappointing period of the season.
Watching Borussia Dortmund thrash Madrid will go some way to mending broken United hearts, but deep down fans may feel their side would have been better suited taking on one of the big German sides. Possibly adding to their three European cups leaving them only one behind Liverpool's five making this one of the truly great seasons for the Red Devil's.
Take nothing away from Manchester United, this has been a successful season for them, clinching a 20th Premier League title, sweeter still knowing they took it from the rich hands of their noisy neighbours. However, that disappointment in Europe will still haunt the United faithful.
Where does this season rank among your favourite United campaigns? Comment below.
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