It's claimed Chelsea can re-sign the midfielder for a set fee before the clause expires at the end of the year.
Eberl, however, told Express: "There is no clause. There is also no deadline. Nothing was written into the contract."
But the director also admitted: "But we also need to make no secrets about it: If we get from Chelsea a top player, then Chelsea has of course again and again the possibility in whatever form, to think about this player.
"But for now they've actually not..."