The club captain is in the final year of his contract and as yet no extension has been agreed.
Koren, who has made over 100 appearances for the Tigers in three years, believes that this could now be his last season with the club.
"It is true that this is my last season, my contract is running out," he told TV Slovenija.
"After that, everything is open. In football you never known what will happen in the future."
Koren started in the league win against Norwich City on Saturday.