Alexander Isak and Newcastle United are now embroiled in a war of words following the Swede’s shock statement.

Explained: The Swedish striker is determined to leave St James’ Park and Fifa’s amendments to article 17 give him an exit route next summer that would potentially cost Newcastle millions of pounds

You've probably seen coverage of the Alexander Isak transfer saga, but you are probably far less familiar with a little-known FIFA rule called Article 17. It could be the key to unlocking Isak's future.