Bayern Munich and Borussia Dortmund reportedly agreed in January 2013 that Robert Lewandowski wouldn't be sold to Real Madrid.
Dortmund agreed to allow Lewandowski to eventually go to Bayern on a free transfer under the condition that Marco Reus wouldn't be pursued as well.
Reus has a €30 million buyout clause in his contract.
Dortmund’s Hans-Joachim Watzke and Bayern’s Karl-Heinz Rummenigge agreed to the deal, but Rummenigge has since spoken openly about buying Reus.
Via Der Spiegel