Duane Vermeulen has joined up with the South Africa squad after a quicker-than-expected recovery from injury as they prepare for the deciding Test against the British and Irish Lions.
Vermeulen had ankle surgery in June and was expected to miss the entire series.
"It will be great to have him with us," said Springboks coach Jacques Nienaber.
His recovery is similar to that of Lions captain Alun Wyn Jones, who joined up with the squad just 18 days after dislocating his shoulder.
Nienaber added that the 2019 World Cup winner "will be medically assessed as soon as possible" as South Africa prepare for Saturday's series decider in Cape Town.
"We will never risk a player who is not 100% fit, but he brings experience to the squad," he said.
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South Africa will also find out on Monday the extent of the shoulder injury suffered by Pieter-Steph du Toit in Saturday's second Test.
Flanker Du Toit was hurt after a late tackle by Lions winger Duhan van der Merwe and was clearly in pain before leaving the field during the first half.
South Africa beat the Lions 27-9 in a fiery encounter to level the three-Test series and set up a decider next weekend.
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