Cologne - It is one of the fiercest rivalries in world football: Borussia Dortmund and FC Schalke 04. The Revierderby brings emotions to boiling point, but the clubs and their fans share a common identity, forged as they were in the foundries and furnaces of the Ruhr district - Germany’s industrial and footballing heartland.

It’s a region founded on hard-work, dedication and a deep sense of loyalty. Perhaps more than anywhere else in Germany, fans in the Ruhr district expect to see these values conveyed on the pitch. Commitment to the cause is indispensable if a player is to endear himself to the supporters.

Usually, that would be rendered impossible if a player were to join his team's biggest rivals. Yet, by adhering to the fundamental Ruhr principles, some players have managed to cross the tricky divide and find acceptance on the other side.

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