Sky Sports understands that Dinamo Zagreb striker Duje Cop is attracting interest from clubs across Europe.
Benedikt Howedes has been linked with a move to Arsenal, among others, but he is expecting to remain at Schalke.
Schalke have signed goalkeeper Christian Wetklo on a one-year contract to provide cover for number one Ralf Fahrmann.
Tottenham strikers Emmanuel Adebayor and Roberto Soldado scored as Spurs wrapped up pre-season with a win over Schalke.
Newcastle United's summer signings impressed as they eased past Schalke with a 3-1 friendly win at the Veltins-Arena.
Bayer Leverkusen have signed Greek defender Kyriakos Papadopoulos from Schalke on loan until the end of the season.
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