However, he hopes his captain can be persuaded to stay.
"As I said the other day, the only person who can decide his future is Leo himself," Koeman said.
"As a club, as the coach, I would like him to stay for many more years and will try to give him good sensations to be happy because we need him.
"If he is happy like he is at the moment, he gives so much quality to the team. He also helps the morale and brings good energy. He helps the team.
"But as I have said before, only one person can decide the future in this case and it's in his hands."