Scrum-half Kieran Marmion is facing a battle to be fit for the start of Ireland's Six Nations title defence.
Marmion, 26, started Ireland's 16-9 win against New Zealand in Dublin but he was replaced in the 59th minute.
The Connacht player will have surgery this week on an ankle injury and the province say he will be out of action until February.
Grand Slam champions Ireland begin their 2019 Six Nations campaign against England on 2 February.
Marmion, who appeared to suffer an ankle injury against Argentina earlier this month, was one of seven players released from the Ireland camp on Monday and he will now miss the remainder of Connacht's European Challenge Cup pool games and the inter-provincial matches against Leinster, Ulster and Munster in late December and early January.
Flanker Sean O'Brien is also targeting a Six Nations return as he recovers from the broken arm he sustained against the Pumas.
Leinster's Luke McGrath and Ulster's John Cooney will compete for the starting scrum-half role in Ireland's final autumn international against the United States after Marmion had started the matches against Argentina and the All Blacks in the absence of first-choice number nine Conor Murray.
In a further blow to Connacht, prop Conan O'Donnell has had an operation on a hand injury and will be sidelined until next month while Eoin McKeon, Craig Ronaldson and Conor McKeon are long-term absentees.
Connacht head coach Andy Friend has taken a squad of 25 players to South Africa for their back-to-back Pro14 matches against Southern Kings and Cheetahs with fit-again Paul Boyle, Matt Healy and Peter McCabe all part of the travelling squad.