Borussia Dortmund CEO Hans-Joachim Watzke has warned clubs interested in Jadon Sancho that they will have to pay full price to sign the winger this summer.
The 20-year-old has emerged as one of Europe's most promising players since his breakthrough in Germany, having joined BVB from Manchester City in 2017.
Manchester United and Chelsea are reportedly ready to act on their interest this summer, while Liverpool, Barcelona and Real Madrid have all been linked to him, too.
Any deal for Sancho is expected to amount to at least £100 million ($125m), though there has been speculation that the Covid-19 pandemic will see transfer fees drop when business resumes.
Watzke, however, says Dortmund will only let Sancho leave if he demands it and maintains any buyer will have to match the club's valuation.
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"Even before the coronavirus outbreak, we said that we would prefer that Jadon stays with us. At the end of the day, however, you always have to respect what the player wants," Watzke told Bild am Sonntag.
"I'll state clearly, that no rich club should think that during this existential crisis they can steal players from us. We don't have to sell anyone for less than they're worth."
European football has ground to a halt due to efforts to contain the spread of coronavirus and there are concerns over the financial consequences as the crisis continues.
Juventus and European Club Association president Andrea Agnelli warned this week that the game faces its biggest ever threat.
Clubs and their employees are mired in uncertainty, but Watzke says Dortmund will do all they can to support their members in such difficult times.
"I am responsible for more than 150,000 members, for our shareholders, but above all for 850 BVB employees and their families," he added.
"We are one of the largest employers in the city. It's about ordinary workers, not about football millionaires.
"Our travel agency no longer sells trips, our events and catering company no longer organises events and certainly not catering.
"Nevertheless, we said: As a sign of BVB unity, there will initially be no short-term work. For me, that means responsibility and solidarity.
"We can not disregard the fact that the Bundesliga clubs are and will remain competitors. And of course, we are solidary if someone has got into an imbalance through no fault of their own. That cannot be excluded."