Blues centre Sonny Bill Williams is set to undergo knee surgery that will keep him out of action for at least six weeks.

Williams sustained the injury against the Stormers a fortnight ago and missed their following match against the Waratahs.

The Blues had hoped Williams could be fit to face the Chiefs in Hamilton this week, but coach Leon MacDonald confirmed on Thursday that the 33-year-old needs to have a minor operation to fully recover.

‘It’s a big blow, I feel sorry for him. It’s unfortunate for him,’ MacDonald said. ‘The knees have caused him trouble in the past, but he’s pretty driven to make sure he recovers well from this injury and gets back on the field.

‘If he still wants to play later on, he’s the sort of guy who you would never write off. He’s a pretty determined guy, and this year he wants to make the World Cup squad, and be a part of that obviously.’

Photo: Hannah Peters/Getty Images