Victor Wanyama is set to miss Thursday night's Europa League play-off against FC Midtyjlland.
The Kenyan midfielder, who has recently been linked with Tottenham, will not make the trip to Denmark due to a stomach infection.
Saints boss Ronald Koeman revealed the news at his pre-match press conference: "Victor has not travelled because of a stomach infection.
"I hope that he will be available for the weekend, but we have to wait."
Southampton drew 1-1 with Midtyjlland at St Mary's last week ahead of the return bout at the MCH Arena in central Denmark tomorrow.