Ronald Koeman admitted he decided to switch to a back four against Chelsea after losing Nathaniel Clyne to injury.

Koeman already knew he would be without left back Ryan Bertrand, who was ineligible to face Chelsea, from whom he is on loan at St Mary’s this season.

Clyne missed the game against the Blues after an injury to his foot sustained in the win over Crystal Palace, which is also set to sideline him for the matches against Arsenal and Ipswich in the coming days.

After back-to-back wins with three centre halves, Koeman made another change to the formation for Chelsea and once more it paid dividends.

He said: “We didn’t have Ryan Bertrand, we didn’t have Clyne and players make a system.

“That was the reason to change that and I think the key was that we had enough players in the midfield to have that organisation that you need to play against them.

“They are fantastic and players like Hazard, Fabregas, in a split second they can change the game and that as well was one of the reasons to change the system.”

Koeman handed a first Premier League start to Matt Targett, who performed admirably at left back, and moved Maya Yoshida to right back.

The Japan international, who heads off to play for his country at the Asia Cup after the New Year’s Day fixture at Arsenal, was taken off in the second half having struggled against Eden Hazard.

“I am very satisfied about Maya,” insisted Koeman.

“He was very tired in the second half, he had a yellow card and it’s so difficult to play and have a good defence against players like Hazard.

“I had to change him on that moment but he’s back on the team, playing well, and he will stay for the Arsenal game and then he can go and play for Japan.”

Morgan Schneiderlin will be suspended for the Arsenal game after picking up a late red card for a second caution in the game, but Koeman is happy to still have Sadio Mane available after he scored his second goal in as many games.

“He’s feeling comfortable in that position behind Graziano,” said Koeman.

“I think he is a little bit more freedom to have his movement.

“He’s very fast and two typical Mane goals how he scored against Chelsea and against Crystal Palace.

“Still he is in because he has to play the Africa Cup.

“I am happy about his performance but the player is playing better and with more confidence than he had in the beginning.”

One of the major talking points of the game was Cesc Fabregas getting booked for diving when he wanted a penalty but Koeman said: “I don’t know I have to see it back. I have to watch that moment.

“It’s maybe a penalty and if it is then they can be disappointed about that decision but it’s part of football.”