South Africa winger Sbu Nkosi is a major doubt for the Rugby Championship after suffering an ankle injury that could see him miss up to 12 weeks.

Nkosi impressed in his first three international appearances during the Springboks' series win over England in June, scoring two tries.

The 22-year-old returned to Super Rugby action with the Sharks but the team confirmed on Thursday that Nkosi has suffered a syndesmosis sprain in his left ankle, leaving him doubtful for South Africa's next international outing.

Nkosi is expected to miss up to three months with the injury, with the Sharks hopeful he could be back in eight weeks.

An early return would mean only missing back-to-back matches with Argentina, although the wing would be lacking in match fitness for a clash with Australia on September 8.

Should he miss the full 12 weeks, South Africa will only welcome him back on October 4 – just two days before their final match with New Zealand in Pretoria.