Schalke 04 striker Klaas-Jan Huntelaar has a reported €15m (£12.3m) release fee in his new contract with the Bundesliga outfit.
The Dutch international recently penned a two-year extension at the Veltins-Arena after his old deal came within six months of expiring.
However, according to German newspaper Bild, Die Konigsblauen could still lose him against their will should a team activate the clause.
Huntelaar, who has scored five goals in 17 league games this season, has previously been linked with moves to Arsenal and Liverpool.
The 29-year-old has been at Schalke since 2010.
