Rory Best has emerged as Ireland's latest injury worry.
The Ulster hooker will engage in what Team Manager Mick Kearney called "modified work" in the days ahead to prepare for a powerful South Africa.
Best's calf is a serious enough impediment for coach Joe Schmidt to call in his provincial colleague Rob Herring.
There are four hookers at camp this week, Leinster's Richardt Strauss and Sean Cronin working with new man Herring as Best goes about proving his fitness.
The ability of tight-head Mike Ross to overcome his groin injury prompted Schmidt to invite Leinster's Tadhg Furlong to join Munster's Stephen Archer and Connacht's Rodney Ah You as a second pod of four.
"Mike did some running and multi-directional work as well as static teamwork on Friday and will be introduced to full training over the next few days," said Kearney.
"He will be closely monitored. The prognosis is positive. We are reasonably confident he will be available for selection."
Ross is notoriously slow in climbing up to match sharpness. He has often mentioned in the past how he has to play consistently to build up his endurance.
The Leinster tight-head is right there with Marty Moore as a man who has to shift weight to get into playing condition.
Ireland's anchor man scales in at a playing weight of 20 stones (127 kilos).
He hasn't been able to take the field since the PRO12 defeat by Munster on October 4th.
An Ireland front row without Best and Ross, especially at scrum time, would have the south Africans licking their lips.
Full-back Rob Kearney, centre Gordon D'Arcy, loose-head Jack McGrath, centre Stuart Olding and wing Tommy Bowe are all scheduled for full training programmes in the lead-in to Saturday's international.