Swansea boss Paul Clement to BBC Sport: "In the end you always get what you deserve but the scoreline is harsh. One to 79 minutes was one goal. I made some changes to put offensive players on but we got in a mess defensively and at 2-0 we were vulnerable. You have to have belief you are still in the game but we gave the ball away and played to their strengths. They are dangerous on the counter and we were punished.
"I will make sure the players do not let this affect confidence too much against a team competing for the title this year. We have to brush ourselves down and prepare for the League Cup next week.
"There was a good atmosphere around the stadium and we started brightly. Generally, our shape was sound but the way it unfolded was disappointing. Move on quickly from this.
"We want to do business in the transfer window and it is clear to see we need quality in."
Ex-Celtic and Wales striker on BBC Radio 5 live
Clearly the opposition will get tougher for Manchester United.
But in terms of the first two games they've been faultless. In that three or four minute spell where they took the game away from Swansea, they were devastating.
4-0, another clean sheet and eight goals in two games. Will there still be United fans who are not happy?
Manchester UnitedCopyright: Getty Images
More from Manchester United manager Jose Mourinho: "Happiness in our play. It happened to me so much with my teams, you winning 1-0 and you can can concede. There was no need to close the door, just let the horses run freely.
"Anthony Martial is working hard. He is confident. The French language connection is there to help him a lot and get to the level we know he can be because the potential is huge."
Manchester United boss Jose Mourinho speaking to BBC Sport: "During almost 90 minutes, I don't say 90 because there was a moment when they had a chance and we lost a little bit the confidence. They were waiting with class, calm and consistency for the moment to kill the game.
"Swansea played with five in the back and they had a moment when they felt they had to change and when they did we had more space and killed the game.
"I felt in control, if you had a chance to look at me and my body language I think you could see that. Football is football and when you make a mistake you can concede so I never felt totally relaxed. I had players on the bench who could help me."
- SMS Message: Can everyone please just stop calling United champions elect. We are two matches in let's not take the mick. from Peter, Manchester
Khristian: 2 games 3 late Goals , Proof that United are Now Ruthless! last season its a draw while playing the same way... small margins
Sho Rahman: All goals aside a shout out for Phil Jones please. Absolutely immense again.
Matt Salisbury: Two good results but let's not get carried away - much bigger challenges to comeCopyright: Getty Images
Ex-Celtic and Wales striker on BBC Radio 5 live
Swansea need a lift.
They need players to come in the door; Paul Clement, I am sure, will have his eyes on several players.
But you cannot keep losing your best players every year. We saw how close Swansea came to going down last year. They lost Ashley Williams last summer, Wilfried Bony the season before.
Now they've lost Gylfi Sigurdsson, you cannot keep recovering year in year out when you sell your best players.
There's money here for sure.
Two goals each for Paul Pogba and Anthony Martial so far this season.
Daniel Shack: Anyone remember how City started last season? #justsaying
Bob Moss: Is it too early too say the Manchester derby will be the title decider, everyone else playing for European places.
Dan Evans Media: I'm calling it...Man United... champions elect already.Swansea played pretty well for 80 mins but United are a different level.
Manchester United midfielder Paul Pogba, speaking to Sky Sports: "We've had a very good result, 4-0 again with a clean sheet, We want to carry on on this road.
"We are more confident [than last season]. We know each other more. We work for each other and I think that is easier for us."
Manchester United winger Henrikh Mkhitaryan, speaking to Sky Sports: "It was a tough game, especially in the first half. We had passion, we did what we had to do. The second half became much easier because they played with more defenders and that left space.
"Team spirit. We also have a little luck with the chances we are creating."
Manchester United have scored 4+ goals in their opening two league games of a season for the first time in 110 years (1907-08).
Reaction to come from players and managers.
Henrikh Mkhitaryan says Swansea going from a back five to a back four in the second half changes the game.
The United players are enjoying this victory.
Anthony Martial has Eric Bailly in a playful headlock, while Paul Pogba 'dabs' towards the travelling supporters.
Never dab too early, Paul.Copyright: Getty Images
Statement of intent.
Swansea looking for a consolation, but Jordan Ayew's daisycutter from 30 yards goes wide.
By the way, in amongst all them goals, Ander Herrera came on for Henrikh Mkhitaryan.
Into injury time.
Swansea boss Paul Clement looks on ruefully.
BBC Sport app users may have to click view more to see this tweet.
£89m + £75m = goals galore.Copyright: Reuters