After Romelu Lukaku’s 20th-minute finish gave United the lead, they struggled to perform with the same fluent authority that has inspired their fine start to the season as Southampton significantly improved – albeit without creating an equalizer.
That they remained goalless owed as much to the hosts’ long-term struggles in the final third as the form of Bailly and Jones, which comes after the years of instability that followed the departures of Nemanja Vidic and Rio Ferdinand.
United also spent £31million recruiting Victor Lindelof during the summer, amid the expectation that he would succeed Jones, who has since regularly started for England, and asked of their performances, Mourinho responded: ‘Very good.
‘And also (substitute Chris) Smalling. We did for 20 minutes what the majority of the Premier League teams are doing, which is to play defensively with five at the back.
‘We did that for 20 minutes. We had chances to kill the game and score the second goal, but didn’t.
‘Then, Southampton were strong. I felt the manager (Mauricio Pellegrino) enthusiastic, exciting, risking bringing on two strikers like (Manolo) Gabbiadini and (Charlie) Austin to play direct, and also in a style that isn’t normally their style.’
Saturday’s victory follows four others in the Premier League that have been by considerably wider margins, and Mourinho, who was dismissed late on for appearing to clash with fourth official Mike Jones, said: ‘It’s better to win 5-0 than 1-0. We wanted to win also 5-0.
‘But it’s not always possible. We had opportunities in the first half to score the second goal and then the game is different.
‘Lukaku and (Ander) Herrera, too, and if we’d done that I would have brought on (Antony) Martial and (Jesse) Lingard and go for a different result. But credit to Southampton and to Pellegrino.’
Southampton has so far failed to score in five of Pellegrino’s seven fixtures since his summer appointment as Claude Puel’s successor.
It was a lack of goals that contributed so much to Puel’s sacking, but Pellegrino, 45, said: ‘In general we controlled the game against a team who are really difficult to control, even when they are defending because on the counter-attack they are really good.
‘They have pace and, in direct play, are really strong. But we did 90 percent really well. Against this type of team, you have to play really well, really close to ‘excellent’, to win.
‘They realized we were playing well. The best teams in the world adapt their players to every single situation.