Three-time European champions United have struggled on the continental stage this season, going out in the group stage of the Champions League before losing at home to Ajax last month in the final 32 of the Europa League.

Fortunately, a 2-0 first-leg victory in Amsterdam ensured they set up up a last-16 meeting with Bilbao in European club football's second-tier tournament at Old Trafford here on Thursday.

But United's failure to win three of their four home games in Europe this season has given the Spanish visitors hope of springing a first-leg surprise.

"It's a game in which we need to wake up, there's no question about that," said United manager Ferguson here on Wednesday.

"Some of our European form this season has been disappointing. But it's an opportunity to progress and we need to take that opportunity. But we'll need a very, very good performance.

"I don't know if we've struggled because we've been making too many changes in these games," added Ferguson, whose English champions are currently two points behind leaders and local rivals Manchester City in the Premier League.

"But we made mistakes in the group stages of the Champions League, so it's our own fault. It's disappointing but tomorrow (Thursday) we'll field a strong team and hopefully that will make a difference."

United goalkeeper David de Gea will be facing Spanish opponents for the first time since his £18.9 million ($29.8m) pre-season move from Atletico Madrid.

De Gea has had his critics since replacing the retired Edwin van der Sar at United, but he believes he is finally adapting to life at Old Trafford.

The 21-year-old Spaniard was dropped recently but has responded with some outstanding saves since returning to the team.

"I did receive one or two bits of criticism at the start of the season," de Gea said here on Wednesday.

"It only serves to make you a stronger person, it encourages you to keep fighting and keep working hard.

"The important thing is not to let yourself get down. It could almost be a positive thing. You can turn it around and through the hard work, I've waited for my chance and grabbed it.

"Fortunately I'm now showing some good form, which I hope will continue through to the end of the season.

"The time I spent on the bench when I was out of the side was when I could reflect and think hard and almost re-group.

"It made me more determined so when I did get my opportunity back in the side, it was important I grabbed it with both hands.

"The thing now is to keep on this good form because you know one slight slip-up, you've got players waiting in the wings to grab their opportunity."

Veteran United midfielder Paul Scholes missed an open training session on Wednesday but is set to feature along with Brazilian Anderson, who has been sidelined with a knee injury.

"We just gave Paul a day off," explained Ferguson. "We gave him a rest.

"He was indoors. Paul and Ryan (Giggs) don't train every day. We give them certain days off."

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