Borussia Dortmund have told injury-hit Manchester City target Ilkay Gundogan to either leave at the end of the season or sign a long-term contract extension.
After Bayern Munich announced on Tuesday they have signed Borussia's captain Mats Hummels on a five-year deal, Dortmund are looking to keep hold of their other stars as they plan for next season when Borussia will be back in the Champions League.
Midfielders Gundogan and Henrikh Mkhitaryan have been linked to Premier League clubs with City and Chelsea respectively reported to be interested.
Gundogan's agent met with City's director of sport Txiki Begiristain in Amsterdam in March and reports in the German media say the deal is set to be finalised at the end of the season.
But the situation has been complicated after Gundogan, who has a year left on his current Dortmund contract, dislocated his knee in training last week.
The injury has ruled him out of next month's European championships in France with Germany and no date has been given as to when he can play again.
"I have spoken to him, he's very down after another serious injury. He knows we'll stand by him," Dortmund's CEO Hans-Joachim Watzke told local newspaper the Ruhr Nachrichten.
"There are two options, which we have discussed with Ilkay for a while.
"Either he leaves or he stays and extends his contract, but it must be long-term."
Gundogan is injury prone and missed most of the 2013-14 season, including Germany's World Cup triumph, with a persistent back injury.
In recent seasons, he has only signed year-long extensions, but Borussia now want a longer commitment while Watzke says discussions with Mkhitaryan are still ongoing.
Meanwhile, Hummels will play his final league game for Dortmund at home to Cologne on Saturday and Watzke says the farewell will have to be handled sensitively.
The Germany centre-back was booed and jeered during Dortmund's previous home game after news first broke that he would join Bayern for next season.
Hummels has become the latest Borussia star, after Mario Goetze and Robert Lewandowski, to join Bayern, but Watzke hopes there will be no more negativity from the Dortmund fans.
"I hope and wish that it'll be the case," said Watzke.
"I'd be happy if the whole club showed how big we are, there is no reason for bitterness, we respect his decision, also when it's a pity."
According to reports, the sale of Hummels will make Dortmund 38 million euros ($43.3m) and Watzke has said the team will be "just as good as this year" as they look to sign a replacement.
Austrian international Aleksandar Dragovic at Dynamo Kiev has expressed an interest in joining Dortmund while Germany defender Shkodran Mustafi at Valencia and Real Madrid's Raphael Varane are also reportedly on Borussia's wish list.