Barcelona coach Pep Guardiola fears Manchester United have a secret weapon tonight.
Guardiola admits that one player who will worry his defence is United's speedy Mexican forward Javier Hernandez, better known as Chicharito.
Guardiola said: "He is a huge surprise, amazing. The way he plays in space and arrives in the area.
"He has incredible movement and shoots quickly, so United have bought an enormous player."