Mauricio Pellegrino says Virgil van Dijk is being chased by the biggest teams in the Premier League and does not know if he will stay at the club in the January transfer window.
Defender Van Dijk made his Saints return as a late substitute in Saturday's 1-0 away win over Crystal Palace, after handing in a transfer request last month in a bid to force an exit.
That came after the centre-back was heavily linked with a move to Liverpool, whose interest ended with an apology after Southampton threatened to report them for allegedly making an illegal approach.
"Around the player there is a lot of interest," Pellegrino told reporters of Van Dijk.
"You know how football is, it's a big business as well as a game. We have to accept that. Around him it is the same situation.
"We never know how the market will be in January. We can bring in some players, every single squad can improve. We have got people who are working to improve our squad all the time.
"And for the other teams it's the same. They will push to bring the best players and Virgil is one case. He's one of the best players in the Premier League.
"It's normal that the biggest teams in the Premier League want to buy him."
For the time being, Pellegrino's focus is limited to on-pitch events, with Saints sitting on eight points from their first five league games this season.
He added: "Now we have to leave aside this situation. Now everything is normal.
"Now, for me I've got this group of players and I will try to push them, to work with them, to help them, to improve every single day."