Manchester United's hopes of Champions League glory were dealt a blow on Wednesday after an own goal handed Barcelona a 1-0 away win in the first leg of the quarter-finals.
The Catalan giants took the lead after just 12 minutes after an early header from Luis Suarez deflected off the shoulder of the home side's Luke Shaw.
Initially deemed off-side, it was allowed after VAR.
To add to United's woes, Shaw was then booked eight minutes later for obstructing Lionel Messi.
A yellow card means the defender will now miss the second leg.
Despite coming back as the stronger side in the second half, United failed to equalise.
After the match, their coach Ole Gunnar Solskjaer said: “There were pluses and negatives. We started sloppy and a bit nervous.
"But after their goal we did well. We got wide, got crosses in the box. Sometimes those crosses end with headers on goal, sometimes you miss them.”
Solskjaer's side will be hoping for a miracle similar to the one that saw them overturn a 2-0 first-leg deficit to eliminate Paris Saint-Germain on away goals in the last 16.
But Barca have not lost at home for 30 games in the Champions League since 2013.
Despite not being at their best, Barca comfortably held on to take a precious away goal back to the Camp Nou for the return leg.
"Playing here is always difficult because it is a majestic stadium, with history, a great atmosphere and the fans push them on," said Barca defender Gerard Pique, who played for United between 2004 and 2008.
"They pressed but I think we controlled the game well. We were strong at the back and looked to counter-attack. It was an even game but we took our chances."
The second leg in Spain next Tuesday will determine which team make the final four.
