IRELAND team manager Michael Kearney has admitted it is "difficult to say" whether Rory Best will face South Africa after picking up a calf problem.
Head coach Joe Schmidt will be desperate for Ulster hooker Best to be fit for Saturday's Springboks clash in Dublin given Ireland's raft of front-row injuries.
Best (right) went through "modified work" in training yesterday, with his progress to be monitored throughout the week.
Ireland must face the big-scrummaging Springboks without props Cian Healy, Marty Moore and Nathan White, while tighthead Mike Ross is still fighting for fitness after groin trouble.
"Rory Best has a tight calf that will be monitored all week," said Kearney.
"It's probably a little bit more difficult to say with Rory, but he will do modified work and be monitored closely.
"Mike Ross went through some running and multi-directional work as well as static team work on Friday, and will be introduced to full training over the next few days.
"He will be closely monitored but the prognosis is positive and we are reasonably confident he will be available for selection."
Johnny Sexton is expected to train fully all week despite suffering "tightness in his thigh", with Kearney confirming Racing Metro agreed to limit his French Top 14 action to 40 minutes at the weekend.
Gordon D'Arcy, Rob Kearney and Jack McGrath are all expected back in full training this week, while Stuart Olding and Tommy Bowe have come successfully through concussion protocols and will be available too.
"We don't have a concern over Johnny, he will be expected to play
full part in the sessions over the week," said Kearney.
"It had been prearranged that he would come off at the weekend, he was always going to play a limited part in the Racing game."
Meanwhile, British and Irish Lions scrum-half Conor Murray urged centres Robbie Henshaw and Jared Payne not to become "bogged down" by following Brian O'Driscoll into Ireland's 13 shirt.
Kiwi boss Schmidt has confirmed Connacht's Henshaw and Ulster's Payne will battle it out to replace the now-retired O'Driscoll at outside centre.
Team manager Kearney said there had been no IRFU talk of retiring the 13 shirt in a USA sport-style gesture of respect to O'Driscoll.
Munster half-back Murray then backed Henshaw and Payne to relish the challenge of putting their own stamp on the Ireland back-line O'Driscoll dominated for 15 years.
"There's been much talk of it, we had all that chat last year throughout the whole season, the long farewell," said Murray.
"We're pretty much used to that now and there are opportunities for lads to fill into that famous jersey.
"There will be pressure on them, but they're going to have to be their own men, and not be too bogged down by the title of that jersey.
"It's something the public will talk about but within our squad we know the players we've got.
"So we're not going to dwell on that too much.
"I think they see it as an opportunity, they are two really good players and they bring a lot of different things to the table.
"They will be hugely influential if they do get a chance in there.
"They are going well in training, so it's up to Joe who he gives the shirt to, but whoever gets it, I'm sure they'll do a great job."