Man Utd takes on Barcelona in the opening leg of their Europa League play-off, and here are five things to watch for at Camp Nou.

How will the back four cope?

The relocation of Luke Shaw and recall of Tyrell Malacia at Leeds indicated both will start at Camp Nou. Erik ten Hag swears by a right-footed and left-footed central defensive partnership and Shaw has fared favourably on the four occasions he has moved inside this season.

Yet he is likely to encounter the most prolific No.9 on the planet in Robert Lewandowski. Shaw should at least have the benefit of Raphael Varane alongside him. Varane has played against Lewandowski when he was at Borussia Dortmund and Bayern Munich, as well as at the World Cup in December.

Casemiro’s biggest test?

Casemiro will return for United

Casemiro has been one of the outstanding midfielders in the Premier League this season and is a veteran of 19 Clásicos. In Pedri and Gavi, Barcelona have heirs to Andres Iniesta and Xavi, while Frenkie de Jong was identified by Ten Hag as United’s ideal linchpin until the funds set aside for his signing were spent on Casemiro.

No United fan is lamenting De Jong’s wage deferral that led to them moving for Casemiro. United discovered how pivotal Casemiro is in the defeat at Arsenal and draw with Leeds. His duel with De Jong is a fascinating sub-plot this evening, especially as Ten Hag has not closed the door on a second pursuit of De Jong.

Weghorst or Rashford?

This time last year, Marcus Rashford was on the bench for United and Anthony Elanga was starting ahead of him. Rashford is one of the first names on the teamsheet again and he is one goal shy of equalling his season-best tally of 22 in 2019-20.

Wout Weghorst claimed an assist and was denied a goal by an errant Video Assistant Referee at Leeds but it was another weak performance and the Dutchman now has an unflattering one goal in eight United games.

Weghorst could be a handful for Ronald Araujo and Andreas Christensen but it feels only a matter of time until Ten Hag switches to a more fluid front three with Rashford at its apex.

Garnacho rewarded?

If Weghorst keeps his spot then Alejandro Garnacho may have to settle for the role of game-changer for a second match running. The last time the Madrid-born winger played in Spain he started and scored his first United goal against Real Sociedad.

Garnacho took his third goal for the club classily at Leeds on Sunday and Ten Hag’s man-management of the 18-year-old was impressive in a week where he squandered two presentable opportunities with United 1-0 down to Leeds in their first fixture.

Camp Nou hoodoo

For a stadium that arguably stirs the soul of United supporters more than any other away from Old Trafford, United have not actually beaten Barcelona at their gladiatorial ground.

United lost 2-0 on their first visit to Camp Nou in the European Cup Winners’ Cup in 1984, there was the 4-0 drubbing to Johan Cruyff’s ‘Dream Team in 1994, the spellbinding 3-3 in the Champions League group stage in 1998, a methodical goalless draw in the semi-finals in 2008 and a demoralising 3-0 reverse in the quarters four years ago.