Sonny Bill Williams is weighing up the richest contract in the history of either rugby code after a jaw-dropping offer to switch back to the 13-a-side game from Super League-bound club Toronto Wolfpack.

Williams' tilt at another Rugby World Cup triumph with New Zealand was stopped in its tracks by Eddie Jones's England in Japan on Saturday and the 34-year-old is now preparing to turn out for the All Blacks in the tournament's third-place play-off against Wales.

Sonny Bill Williams is set to become the highest paid player in the history of rugby and rugby league. Credit:Getty Images

The former NRL premiership winner appeared set to hang up the boots this year but it has emerged the cross-code star has received contract offers in recent weeks which would top any pay packet he has earned throughout his 16-year career.

The Canadian team are prepared to pay Williams as much as $9 million over two years, according to a source with knowledge of the contract negotiation.