Bloemfontein - Cheetahs captain Juan Smith appears set to miss South Africa's defence of their Rugby World Cup title after tearing his Achilles tendon.

Smith left the field inside the first two minutes of the Cheetahs 25-22 Vodacom Super Rugby defeat to the Bulls in Bloemfontein on Friday, and will undergo surgery early next week.

He is likely to be sidelined for between six to nine months, almost certainly ruling him out of the World Cup in New Zealand starting on September 9.

Cheetahs backline coach Hawies Fourie confirmed the news to Rugby365's Jan de Koning, adding that fellow flank Frans Viljoen tore his hamstring and also faces a lengthy spell on the sidelines.

Smith had just returned from a calf strain which ruled him out of the Cheetahs' 24-9 Week 1 loss to the Sharks in Durban.

The Cheetahs lost another key player earlier this week when Springbok hooker and stand-in captain Adriaan Strauss underwent surgery to repair a fractured bone in his hand.

He is expected to be sidelined for between four to six weeks.

The Cheetahs travel to Cape Town to face the Stormers next Saturday in Week 3 of the tournament.