The Croatia international recently criticised the club for failing to sanction a move to Liverpool after the Reds reportedly lodged a £20m bid for the player.
"We have to do and Les Reed has to do what is the best for the club," the Daily Echo quotes Koeman as saying.
"He has a contract, he has to come back this Sunday but I don't know what will happen after this. It's football, there a lot of movements, but first of all we like to keep all that information in the club and not the press and that was not good on his side."
Reports had initially claimed that Lovren was planning on refusing to return to the club for pre-season training.