However, PSG's Julian Draxler is confident that the French champions have the players to put the shackles on the World Cup victor at Old Trafford.
Fellaini said of that contest: "I think Manchester United are the favourites. It's a big challenge to play against him".
"Perhaps it is easier to play this style of football and not the style of football he [Mourinho] asked." . That is my job, after all - to make the difference, to be more decisive.
"When our new coach came in he had a lot of confidence, a lot of determination".
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"We can not forget we have a second leg in Paris so it is not all in or nothing tomorrow", said the German worldwide.
The Frenchman has contributed to 13 goals in his last 10 matches, a hot run of form that includes three braces.
"Well I don't think there's any surprise about Paul Pogba being a key player, he's an incredible player", he said, according to Manchester Evening News.
Co-owner Avram Glazer travelled to Craven Cottage for Man United's 3-0 win over Fulham over the weekend and spoke with both Solskjaer and his agent Jim Solbakken after the game.
The abiding memory Solskjaer took from watching PSG's 2-1 defeat by Lyon the week before last was of "how lightning quick Mbappe is". They had a problem with [Adrien] Rabiot because he is maybe going to leave in the summer and he is a good player for them.
Reporter's view (Matthew Howarth, UEFA.com): Since Ole Gunnar Solskjær's arrival on 19 December, United have claimed more league wins than in the first four months of the campaign under José Mourinho. "It wasn't the best period of my career, or they didn't let me have my best time there", Di Maria said in a recent interview with radio station France Bleu.