Bayern Munich fear Robert Lewandowski could invoke FIFA's Webster Ruling and walk away for nothing this summer.

BILD says Bayern fear that Lewandowski will resort to legal means that no top star has dared to use before.

Article 17 of FIFA's Regulations states any player who signed a contract before the age of 28 can buy himself out of the contract three years after the deal was signed - a fact that Lewandowski's agent Pini Zahavi knows well.

The term has been labelled the 'Webster Ruling' after Andy Webster set the precedent during his move from Hearts of Midlothian to Wigan Athletic in 2006. The rule states that any player that does chose this option, must provide the club with a form of compensation.

If Lewandowski were to terminate his deal, he would only have to compensate Bayern with the salary of his last year of the contract - estimated at €24 million.

This would be considerably less than what Barcelona are willing to offer for the Pole, with the Catalan side said to be ready to fork up a €32m fee.