Manchester United goalkeeper David de Gea has admitted that his side "have to improve a lot" if they are to have any chance of beating Barcelona.
The Red Devils head to Catalonia for Tuesday's Champions League quarter-final second leg on the back of a 1-0 loss in last week's opening tussle at Old Trafford, where they failed to register a single shot on target.
That was United's fourth loss in five matches, but they responded with a 2-1 victory over West Ham United on Saturday.
Even that win was scrappy, though, and De Gea concedes that a lot more is going to be required if his side are to keep their European campaign alive.
"Of course it's difficult, but if you want to be a top team you have to play big Champions League games, and the weekend after it's the Premier League," The Mirror quotes the Spaniard as saying.
"So you have to be focused and ready for a difficult game again. I think today we didn't play well, we have to improve a lot and now we have a big challenge on Tuesday. We will try to fight and win the game. We can go with more confidence after the three points.
"It's a big challenge, a special occasion, in Spain, against Barcelona, a Champions League night, so it's going to be an amazing game. We're happy with the win, but at the same time we have to improve a lot."
Barcelona have never lost a home match against Man United in European competition, with their last such meeting finishing 0-0 in April 2008.
