Morgan Schneiderlin's future at Southampton is back in doubt after the midfielder told the club he was "not mentally or physically ready" to play.
The 24-year-old has been linked to Tottenham but Saints chairman Ralph Krueger has said he is not for sale.
Schneiderlin, who will miss Saturday's friendly with Bayer Leverkusen, has been given two days off to consider his future by manager Ronald Koeman.
The news came on the same day that defender Jose Fonte signed a new deal.
Fonte has signed a contract that will keep him at the club until 2017, with the Portuguese also named as captain for the forthcoming season.
He had been linked with a move to Cardiff City and Koeman said it was vital to keep hold of players such as Fonte and France international Schneiderlin, having already lost six members of the squad in the summer.
Striker Rickie Lambert, midfielder Adam Lallana and defender Dejan Lovren have moved to Liverpool, left-back Luke Shaw has joined Manchester United, Arsenal signed right-back Calum Chambers and forward Dani Osvaldo has joined Inter Milan on loan.
Schneiderlin trained with his team-mates this week as he regains fitness following an extended rest after the World Cup.
He had criticised the club on social media for refusing to let him leave and Koeman admitted the midfielder was not ready to play.
"The situation is difficult, the player makes it difficult," Koeman told BBC Sport.
"I spoke to him with our chairman and the situation has not changed - we don't sell Schneiderlin and he has to accept that.
"Tomorrow he is not in the squad. He said he is not physically and, even more, mentally prepared for tomorrow. On one side I can understand that."
Koeman added: "He will continue as a football player of Southampton. Now it is up to him. If this is still the situation next week then Morgan has a big problem.
"We told Morgan to take two days off and think about the situation because we will not change our minds. This is our decision. So we will see on Monday."
Tottenham have been linked with the player, and Koeman added: "I'm not so much angry because there's some different influences around the player.
"Maybe Tottenham is pressing the player, maybe the agent is pressing the player - it's a difficult situation.
"I understand that situation, I know from my experience how it works but we have to do what is the best for Southampton.
"That is my job and even if I, in some ways, understand his situation I have to do the best for the club and that is keeping these kind of players."
Celtic keeper Fraser Forster is on the verge of joining after Southampton agreed a fee in the region of £10m with Celtic.
The club have already signed defender Ryan Bertrand, midfielders Dusan Tadic and Saphir Taider, and striker Graziano Pelle, with Koeman admitting they were also "interested" in defensive pair Florin Gardos of Steaua Bucharest and Sporting Lisbon's Marcos Rojo.