It wasn't to be for Ole Gunnar Solskjaer back in Barcelona as Lionel Messi sent Barcelona through to the last four.

They will now face Liverpool or porto, while Ajax await Manchester City or Tottenham after another wonderful win against Juventus.

Read the match reports here, and check out the best reaction below.

Manchester United

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Manchester United boss Ole Gunnar Solskjaer on BT Sport: "I have to say Lionel Messi is top quality and he was the difference of course. At 2-0 straight after it was game over.

"He's different class, he and Cristiano Ronaldo are the best players of the last decade, everyone agrees on that one. Messi showed his quality.

"We have to aspire to get to that level of Barcelona, we can get there but we have loads of work to do. If we want to get back to Man Utd's true level, true traditions, we have to challenge Barcelona.

"They were a couple of levels above over the two games. We want to play these games again next year so we have a massive week coming up. There is no point dwelling on what could have been, we have to focus on that week."

Darren Fletcher
Former Man Utd midfielder on BBC Radio 5 live

Man Utd are way off Man City and Liverpool but it's about how they bridge the gap now. Do they go down the route of recruiting the best young talent and try to mould them in the United way rather than buying ready made players who maybe don't have their heart in it?

Scott McTominay did not stop all night and if you can put that work rate and attitude into players who have more ability, that would be great. Roy Keane and Paul Scholes had it but they were world class players as well.

Manchester United

Manchester United midfielder Jesse Lingard on BT Sport: "You can't make errors in these games. We dominated for the first 15 minutes, we had chances and the game could have been different.

"Lionel Messi brought his A-game tonight, he's one of the best in the world. All we can do is move on, it's a big week ahead. We were always underdogs but we had to back ourselves and believe. Chances in these big games are massive."

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Donny van de Beek on Veronica TV: “I knew for sure that I wasn’t offside [when I scored]. I saw that one of their defenders had hung back and was playing me on.

"Everybody is going crazy now. We are in the semi-finals. People would have laughed if we had said that before the tournament started.”

Manchester United

Ole Gunnar Solskjaer to Spanish TV: "We have to rebuild the team and there will be signings this summer."

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Juventus manager Massimiliano Allegri: "Football is vicious, as you concede a fortuitous goal, the fear sets in, we got stretched out in the second half and should’ve had a different approach.

“Ajax fully deserved their result and qualification to the semi-finals.

“I told the president that I will stay. We'll sit down with the club and think about the future.”

Lionel Messi has scored 45 goals in all competitions for Barcelona this season – 10 more than any other player in the top five European leagues.

Image source, Getty Images

Ajax midfielder Frenkie de Jong on Veronica TV: “In the first half they were slightly better and deserved to take the lead. But apart from the first five minutes of the second half, we dominated after the break and were well worth our victory. In fact, we probably should have won by more."

This was Manchester United’s heaviest ever aggregate defeat (0-4) in a two-legged European tie; their previous heaviest was 2-5 vs Milan in the 1957-58 European Cup semi-final and 1-4 vs Atletico Madrid in the Last 16 of the 1991-92 Cup Winners’ Cup.

BBC Radio 5 Live

Former Tottenham and Ajax midfielder Rafael van der Vaart said: "Ajax were much better than Juventus in the second half. We talk about going to the gym and being strong and quick, but they can all play with the ball, and in the end, clever football wins.

"I never thought they could get this far but it is so nice to see everyone scared to play against Ajax. Johan Cruyff is our pride and the best player we've ever had, and I'm so happy two of his teams are in the semi-finals. I'm 100% sure they are going to play each other in the final.

"Frenkie de Jong was one of my favourite tonight even though he didn't play his best game. They play like a team and when you play away in Italy and your goalkeeper doesn't make a save, it is fantastic."

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Ajax centre-back Matthijs de Ligt: "It's bizarre, not normal.I have no words for it!

"We have shown once again that we are very strong and that we can make it difficult for large teams.We have defeated Real and Juventus, two intended title candidates.We are very proud, the supporters are proud, the city is proud.

"I wasn't born the last time we reached the semis."

Roger: To me Pogba is a superb talent... Problem is he knows it. He doesn't think he has to prove it. Alexis gets on the pitch and is lost, doesn't know where he fits in. Phil Jones next Duncan Edwards. I wish.

Lotak: People have seriously underestimated Ajax. They should have beat Bayern in the group stage, should have beat RM at home in the first leg and should have beat Juve in the first leg too. They have been nothing short of incredible in the CL this season.

Darren Fletcher
Former Man Utd midfielder on BBC Radio 5 live

It was 4-0 over the two legs but it hasn't been an embarrassment and it could have been more if Barca wanted to turn on the style.

United shouldn't lose too much heart from this tie and they have to concentrate on the top four now. These players have to show they are part of Manchester United's future in the remaining games of the season.

Manchester United

Image source, Getty Images

Manchester United boss Ole Gunnar Solskjaer on BT Sport: "I have to say Lionel Messi is top quality and he was the difference of course. At 2-0 straight after it was game over.

"He's different class, he and Cristiano Ronaldo are the best players of the last decade, everyone agrees on that one. Messi showed his quality.

"We have to aspire to get to that level of Barcelona, we can get there but we have loads of work to do. If we want to get back to Man Utd's true level, true traditions, we have to challenge Barcelona.

"They were a couple of levels above over the two games. We want to play these games again next year so we have a massive week coming up. There is no point dwelling on what could have been, we have to focus on that week."

Ian Dennis
Radio 5 live senior football reporter at the Nou Camp

When you remember back to Russia and how Paul Pogba galvanised the French effort in winning the World Cup. How often have we seen him do that in a United shirt? He does not reach those high standards week in week out.

Manchester United

Manchester United midfielder Jesse Lingard on BT Sport: "You can't make errors in these games. We dominated for the first 15 minutes, we had chances and the game could have been different.

"Lionel Messi brought his A-game tonight, he's one of the best in the world. All we can do is move on, it's a big week ahead. We were always underdogs but we had to back ourselves and believe. Chances in these big games are massive."

Darren Fletcher
Former Man Utd midfielder on BBC Radio 5 live

Man Utd are way off Man City and Liverpool but it's about how they bridge the gap now. Do they go down the route of recruiting the best young talent and try to mould them in the United way rather than buying ready made players who maybe don't have their heart in it?

Scott McTominay did not stop all night and if you can put that work rate and attitude into players who have more ability, that would be great. Roy Keane and Paul Scholes had it but they were world class players as well.

This is the first season that Cristiano Ronaldo won't be in the semi-finals of the Champions League since 2009-10!

Kim Kallstrom reached the last four that year...

Image source, Reuters