Manager Ole Gunnar Solskjaer’s side will need to pull off another impressive European comeback as they did against PSG in the round of 16, if they are to book a place in the semi-final.
A Luke Shaw own goal gave the La Liga giants the edge.
United go into the clash at the Nou Camp on Tuesday night as underdogs due to current form and result in the first leg.
“Being 0-1 behind isn’t a good scoreline, but we are Manchester United and when you wear this shirt anything is possible,” Mata wrote in his weekly blog.
“It is something that I have already repeated on many occasions, but it is real, and we have experienced it several times this season.
“We are now in what could be the final four weeks of the season and every game is key. You have to mix your desire with responsibility, but you always have to be fully motivated.”
