The Blues have confirmed today that Sonny Bill Williams will be sidelined for up to six weeks, with the cross-code star out of rugby action due to an ongoing knee injury.

The 33-year old is expecting to undergo knee surgery, which will be a major setback with his ambitions to go to his third Rugby World Cup campaign this year in Japan.

TV NZ reports, the All Blacks midfielder suffered the injury against the Stormers last month, while setting up a try for first-five Otere Black.

Blues coach Leon MacDonald says Williams will be a huge loss for the Auckland Super Rugby franchise.