Mourinho's men have been written off at various points this campaign and major questions were asked and decisions queries ahead of each of their last three league games.
Giggs says the criticism started following the 0-0 Premier League draw with Liverpool at Anfield last October.
Rico said in a press conference: "Both for Sevilla and me personally it's an important and special match".
Jose Mourinho has rotated between Ashley Young and Luke Shaw at left back, but following the former's excellent performance on Saturday - when he quelled the attacking threat of Liverpool's star player Mohamed Salah - the Portuguese tactician is expected to keep Young at left back. I know that it is very hard to go through.
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Manchester United go into Tuesday's game as favourites to qualify after their goal-less draw in the first leg, and they have their goalkeeper to thank for holding that advantage.
"I think when a team gets into the last eight the feeling is you are [competing] among the best but anything can happen".
A Sevilla victory would mean qualifying for the quarterfinals for the first time in six decades, and the historic chance has drawn the largest crowd of Sevilla fans so far to attend an away match in the Champions League knockout stage, reports Efe.
"I read some quotes from the worst manager in the history of the Premier League", Mourinho told reporters, according to the club's website, referring to De Boer.
Sevilla were eliminated at this stage past year by Leicester City and they are the underdogs ahead of their first ever competitive match at Old Trafford.