Toprak, who has been strongly linked with a move to Borussia Dortmund, has been at Leverkusen for six years.
Eintracht Frankfurt's Jesus Vallejo has not had contact with Real Madrid coach Zinedine Zidane and says he doesn't know if he will return to the club.
Werder Bremen have said they have no plans to sign Arsenal captain Per Mertesacker on loan.
Mexico international Fabian has starred this season to help his side up to fourth place in the table.
Bayern Munich's Thomas Muller says he does not "enjoy being classed" as a striker and sees himself "as a mix between a midfielder and a striker."
Bayern Munich completed their winter training camp with a comfortable 5-0 win over Belgian side KAS Eupen at the Aspire Academy in Doha on Tuesday.