Jose Mourinho is worried Marouane Fellaini will leave Manchester United in the summer as contract talks continue to drag on.
The 30-year-old has endured a difficult relationship with United supporters at times but has become an influential player under the Portuguese.
That form was recognised as United triggered the one-year extension in Fellaini's contract at the start of the year, but agreeing a deal beyond the summer is proving difficult.
Asked if he was worried that Fellaini would not be here next season, Mourinho said: "Yes, I am."
When asked if there was anything he could do to turn it around, the United boss added: "Nothing. It is a discussion between the player and the board. I am not involved in contracts, in deals. And I respect both.
"I respect the player because the player has the right to decide his future. He finishes his contract, he has the right to decide his future, and I respect the board because the decisions and the discussions are under their control.
"So I just wait, wishing that they will have an understanding but it's out of my control."
Besiktas, Fenerbahce and Galatasaray have been linked with a move for Fellaini, with Paris St Germain also reported to hold an interested in the Belgium international.
Despite the speculation, the 30-year-old is set to be involved when Brighton travel to Old Trafford on Saturday.
However, Mourinho's hopes of having Eric Bailly back for the game have been dashed, while Phil Jones' injury means Marcos Rojo could play again after ending his long injury lay-off in the midweek Champions League defeat at Basel.
"No, (Bailly is) not back," the United boss said.
"Just the evolution was not good enough to have him back for the game, so Bailly is out and Jones are out.
"Rojo played very well. We have to see how he is today. There is no more injury in the frame but fatigue, maybe a player that played his first match maybe he feels it a little bit."