Aston Villa boss Unai Emery has said that Manchester United are the "same level as Barcelona," insisting Michael Carrick's out-of-form side present a "very difficult" challenge.

Villa travel to take on United on Sunday, bidding to extend their five-game unbeaten run while piling the pressure on Carrick, who has managed just one league win all season.

Emery's record at Old Trafford makes for pretty dismal reading, however, having never won there during his managerial career. Villa, meanwhile, have lost each of their last six meetings there in all competitions.

Therefore, on the back of Villa's 3-0 Champions League defeat to LaLiga champions Barcelona, Emery has been talking up United.

"We performed like we planned [against Barcelona] but it was not enough, because the level we were facing, this is the highest level for the Premier League and Champions League matches," Emery said.

"On Sunday, Manchester United -- it's the same level as Barcelona. So this is the work we are trying to set with the players, of course very, very demanding."

He added: "It's Manchester United and we have very clear samples, we didn't win one match there for four years. So it means for us it's very difficult.

"Manchester United is a fantastic club, they are performing very good, last year they achieved to play the Champions League. In the league they started not being consistent, but they should recover their consistency. So it's a very, very difficult match."

Emery, who has confirmed he is in talks over a new contract at Villa, stressed his side will have to be at their best.

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"Old Trafford is a huge challenge -- for me, for the players, for our trajectory here together, because we are not winning there.

"We have had some hard defeats, like two years ago when we were close on the last match, to get to the Champions League, and we lost. We lost it.

"So, it's always very, very difficult there. We must play our best -- in our best individual and collective way.

"So, we have a lot of work to do, and we must compete at the same time."

Information from PA contributed to this report.