Werder Bremen general manager Klaus Allofs has warned any club looking to sign Mesut Ozil that he will play against Sampdoria in the UEFA Champions League qualifying round if he is still at the Weserstadion on Wednesday.
Germany midfielder Ozil has been strongly linked with a move to Real Madrid and Los Merengues have already had a €9million (£7.3m) bid for the player knocked back.
The 21-year-old World Cup star is set to be the subject of a second bid, which Werder are expected to consider.
However, Allofs insists that if another club wants to sign Ozil, then they risk not having him available for European football if a deal is not done by Wednesday.
He told Deutsche Presseagentur: "The facts are pretty clear. If a club is looking to sign Mesut to play UEFA Champions League, then that club needs to make a decision before Wednesday.
"If Mesut Ozil is a player of Werder Bremen on Wednesday, we are going to play him against Sampdoria.
"We have not lined up any plan to not do that for whatever reason.
"It would be up to Real Madrid to show up with the right answer to this all."
On a possible new bid from Madrid, Allofs added: "I am not aware of something like that, a new bid is something I am not able to confirm.
"I am, however, guessing that there might be news on that. I am prepared to receive a new bid, though. If this has taken place, we are going to occupy ourselves with that."
Ozil, who joined Werder Bremen from Schalke, is contracted to the Bundesliga outfit until June 2011.