Ronald Koeman has told his side they won’t win another game this season if they defend as they did in the first half of their FA Cup defeat to Crystal Palace.

Saints welcome Swansea to St Mary’s on Sunday afternoon aiming to banish memories of their 3-2 fourth round loss the previous week.

It was a very uncharacteristic performance from Saints, which included some poor defensive errors.

Given that Saints have let in just 16 goals in 22 league games, it was certainly unexpected that they would concede three at home to Palace in the space of one half of football.

Koeman was very unhappy with what he saw and his warned his team of the consequences of repeating that display.

He said: “We like to go on in the league.

“We have a fantastic run in the league and that confidence we need for the game against Swansea on Sunday.

“We have to defend better than we did in the first 45 minutes against Crystal Palace because that was poor defending, really poor defending. We spoke about that, I was disappointed about that, I was surprised about that because normally it’s one of the strengths in the team with a lot of clean sheets.

“If we defend like against Crystal (Palace) then we don’t win any games more and that we have to realise that.”

Though Saints have some injury problems with Toby Alderweireld, Morgan Schneiderlin, Victor Wanyama and Shane Long all ruled out, they are boosted by the return of Sadio Mane and Maya Yoshida from international duty.

The news is not so good for Swansea, for whom new £3m signing from Saints, Jack Cork, is not able to face his former club while key men such as Gylfi Sigurdsson, Wayne Routledge and Ki Sung-Yeung are unavailable.

They are also still coming to terms with the departure of star striker Wilfried Bony.

“It’s difficult because Swansea had some changes, some important changes in the team like Bony, Sigurdsson who can’t play on this Sunday,” said Koeman.

“More important is ourselves to prepare this game.

“We know the system of them, I like the Swansea team how they play out of a 4-3-3 system with fast players on the wing position and we won in Swansea with a little bit of luck and we know it will be a tough game at home.”