By Pete Jenson for MailOnline
Published: 08:42 BST, 16 April 2019 | Updated: 08:42 BST, 16 April 2019
Barcelona have not lost at home in the Champions League since 2013.
If Manchester United are to progress to the semi-finals they will have to do something the last 30 visitors to the Camp Nou in Europe have failed to do.
Looking at some of the teams who have tested Barcelona this season, Sportsmail asks how their weaknesses can best be exposed.
Be brave in wide areas
Ole Gunnar Solskjaer stands on the pitch at the Nou Camp ahead of the quarter-final
Manchester United train under the backdrop of 'more than a club' at the Nou Camp
Barcelona's 4-3-3 can leave their full-backs unprotected. Earlier in the season a run from deep from Athletic Bilbao full-back Oscar de Marcos saw him put his side ahead at the Nou Camp.
If Ashley Young and Diogo Dalot can get high enough up the pitch to get around the back of Jordi Alba or Nelson Semedo then it could pay dividends.
The tactic has worked even better for opponents using wing-backs. Barca lost away to Leganes and were beaten 4-3 at home by Betis earlier this season – both teams played a 3-5-2.
The Betis defeat owed plenty to wing-backs Junior Firpo and Cristian Tello. Junior scored the first and set up the fourth and Tello set up the second.
Manchester United played this system in the first leg but we barely saw Young and Dalot get forward.
Midfielder Sergio Busquets is still a master of his trade but he has less support these days
This was something United did do well in the first leg to the point where the Spain international picked up a booking and was fortunate not to see a second yellow.
Sergio Busquets is still a master of his trade but he has less support these days.
There is more space between his position and the two central defenders because