Lionel Messi's first-half double led Barcelona past Manchester United and into the last four.
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Barcelona have set up a semi-final date with Porto or Liverpool, Lionel Messi's first-half double guiding the Blaugrana past Manchester United in the sides' quarter-final second leg and completing a 4-0 aggregate success.
Messi, who teed up the only goal of Barça's Old Trafford triumph last week, produced a signature left-footed finish from the edge of the box to extend the hosts' aggregate advantage after 16 minutes, adding a second goal four minutes later when De Gea fumbled his right-footed effort from a similar position.
United's best chance fell to Marcus Rashford, who hit the bar within a minute of kick-off, but the visitors mustered little after going behind and Philippe Coutinho's spectacular long-range finish sealed Barcelona's progress to the last four for the first time since the Catalans lifted the trophy in 2015.
View from the stadium: Graham Hunter
What a remarkable night. Temperature wise there's a chill and for 15 minutes there was something similar down Barcelona's spine. The history books will evoke Messi's brilliance and United's heavy defeat, but initially the stadium and the hosts felt a shiver: it couldn't go wrong ... could it? While the crowd roared and worshipped, the brand of football the Camp Nou witnessed was not one that United have met this season or will again. Impermeable it might not be, but sensational and part of Europe's elite four teams it is.
Man of the match: Lionel Messi
Solskjær said beforehand that United could ill afford to become too preoccupied with stopping Messi. As it was, his charges should have kept a much closer eye on the Argentinian, particularly in the opening 20 minutes. If there was an element of fortune about his second goal, his trademark run and finish four minutes earlier had already put the Catalans on course for a comfortable win against Solskjær's men, who had no answer to the Barça captain's movement and trickery.
0: Barcelona have never lost a UEFA Champions League knockout tie when Messi has scored in one of the two legs.
1: This is the first time United have conceded three goals in a UEFA Champions League match since a 3-2 loss at Wolfsburg in December 2015.
2: Coutinho's second-half strike was his second goal against United in 11 appearances; his only goal in nine games for Liverpool against United (W3 D4 L2) came in the 2015/16 UEFA Europa League round of 16 second leg (1-1).
4: This is the first time in four years – since they last lifted the trophy in 2015 – that Barça have got beyond the quarter-finals.
10: Messi is the UEFA Champions League's outright top scorer this season with ten goals.
15: Barcelona have won 15 of their 24 two-legged ties with English clubs – and eight of the last nine.
24: Messi has scored 24 goals in 32 UEFA Champions League outings against English clubs.
31: Barcelona extend their unbeaten home record to 31 matches (W28 D3), a run that started in September 2013.
2013: Messi's opener was his first in the UEFA Champions League quarter-finals since he struck in a 2-2 draw at Paris in April 2013.
What does it mean?
Barcelona will meet Porto or Liverpool, who hold a 2-0 first-leg lead ahead of Wednesday's second leg in Portugal, in the last four as Ernesto Valverde's side continue a three-pronged trophy tilt. Whoever the Blaugrana face, the first leg will be at the Camp Nou, where Barça are unbeaten in Europe since 2013. United turn their attentions to the Premier League's top-four race and making sure they return to this stage next season.
Nine points clear at the Liga summit, Barça welcome Real Sociedad on Saturday and then go to Alavés in midweek. They also have a Copa del Rey final against Valencia to look forward to, on 25 May.
Next up for United are Everton at Goodison Park on Sunday, followed by title-chasing rivals Manchester City at Old Trafford next Wednesday.