Ronald Koeman has highlighted Southampton's "mistakes defensively" in their 6-1 defeat to Liverpool in the quarter-finals of the League Cup at St Mary's.
The Saints opened the scoring inside the first minute, but Daniel Sturridge and Divock Origi led the turnaround, setting up a semi-final meeting with Stoke City.
The manager told Sky Sports News: "That is not the result we expect. A great start but if you make the mistakes defensively we did in the first half and the top quality of Liverpool, then you can lose.
"The second half is my responsibility. I changed the system, I made the risk of three at the back. The first goal of Liverpool is a throw-in and you see how easily they play, that is not good.
"The have a great energy and they have qualities in the team. We gave them that space, those opportunities and if you give a man like Daniel Sturridge that space he will kill you."
The loss is the first time Southampton have let in six goals at home since 1995.
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