The Red Devils were thrashed with goals from Naby Keita and Diogo Jota followed up by a hat-trick from the in-form Mohamed Salah to seal off the commanding victory.
Maguire has now admitted his side were ‘not good enough’ and that he will assess his own performance while urging everyone to stick together.
Speaking on Sky Sports, Maguire said: ‘First and foremost, apologies to the fans. It’s nowhere near good enough at this club. We are all disappointed.
‘We spoke in the dressing room, I’m here because I have to be here.
‘The only real thing is we have to apologise to the fans. They stuck right with us, singing and chanting at 5-0, but for us as a club we have to do better.’
Reflecting on the game, Maguire said: ‘I think it was too open. I’m not here to analyse the game. We are so disappointed, we gave them too many chances, they were really clinical.
‘Defensively, and I’m a defender first and foremost, conceding four at home at Old Trafford is nowhere near good enough.
‘As a player, I know myself, I will be looking at myself as an individual and the performance of the team, I’m the captain and I lead the boys. We have to come together and stick together.
‘We have to look at each other and look at yourself in the mirror and think, what can you do better? It’s not about looking elsewhere and blaming others.
‘To lose to Liverpool, to lose in any game of football hurts this club. No matter who you are playing. Liverpool are our vials and the way we lost the game, to be 4-0 down in front of your own fans is not good enough.
‘We were in the game at 2-0, the third goal was poor and we can’t concede that third goal and when you’re 4-0 down it’s done. We can’t concede straight away after half-time. We were just too open and they caught us out and the red card makes the game in terms of, we can’t push forward.’
Maguire again reiterated that the performance was not good enough: ‘The term I would use is not good enough. I look at them each day in training, they are doing everything they can but at the moment it’s not good enough.
‘That’s the only way I can put it. I want to apologise to the fans and we want to make sure we stick together.’