Manchester United host Barcelona in the Champions League on Wednesday night for the first leg of this mouth-watering quarter-final tie.
Ole Gunnar Solskjaer's side have tailed off in recent weeks, losing three of their previous four games in all competitions, but last month's historic victory of Paris Saint-Germain should act as a warning for the Spanish champions.
Barcelona go into Wednesday's clash following a crucial 2-0 win over Atletico Madrid, which extended their lead at the top of La Liga to 11 points.
However, as United proved in Paris, anything can happen over two legs and a positive result at Old Trafford is absolutely crucial if they wish to progress to their first semi-final since 2011.