Australia's hopes of a 3-0 series sweep have surged following the withdrawal of South African captain Graeme Smith from the third Test because of a finger injury.

Smith suffered a nasty blow to the ring finger of his left hand during a catching drill at the Wanderers Stadium on Thursday and was rushed to a Johannesburg hospital.

"After an X-ray and a scan as well as a consultation with a hand specialist, he was diagnosed with a severe soft tissue injury to the distal part of the finger," a team statement said.

"He will wear a splint for 10 to 12 days after which an assessment will be made regarding his recovery.

"Proteas vice-captain, Jacques Kallis, will assume the captaincy while Boeta Dippenaar will replace Smith in the team."

Dippenaar, who hasn't played a Test since May last year in the West Indies, is expected to open with AB De Villiers with the struggling Herschelle Gibbs to bat at No.3.

Smith has failed to make a half-century in six Tests against Australia this summer, including the World XI match in Sydney in October. However, his leadership will be missed in a young side battling to cope with the constant pressure served up by Ricky Ponting's men.

Top-ranked Australia beat South Africa 2-0 in Australia in a three-match series in December-January and leads the current series 2-0 with one match to play.

South African coach Mickey Arthur said playing against Australia for six Tests in a row was like fronting up in golf matchplay against Tiger Woods, day after day.

"It's just pressure, pressure, pressure all the time," he said.

Australian captain Ricky Ponting wants to make sure the match is a fitting celebration for opening batsman Justin Langer, who will become the 10th Australian to play 100 Tests.

Ponting achieved the milestone in Sydney in January, hitting twin centuries as he did in this week's second Test in Durban which Australia won by 112 runs after taking the first Test in Cape Town by seven wickets.

Neither side has announced a final team for the third Test, although Ponting said he didn't expect any changes to the Australian eleven.

Australia has won the first two Tests then lost the "dead rubber" on its two previous South African tours, but Ponting said his side was playing well but could still improve.

"The cricket that we've played, South Africa haven't deserved to win a Test match yet and we'd like that to be the case in a week's time when we are flying out of here," Ponting said.

Play starts at 1030am (1930 AEDT).

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