Ireland coach Joe Schmidt is fully conversant with the difference between an epidemic and a pandemic as yet another injury has hit his already-emaciated (only speaking of experience) frontrow resources.

It comes on foot of the news that Connacht's New Zealand-born, Irish-qualified tighthead prop Nathan White has suffered a tendon rupture to his upper arm at a national squad training camp at Carton House.

White's injury will keep him out for 16 weeks, and with Leinster duo Cian Healy and Martin Moore and Munster's James Cronin all sidelined, it means there are now four props unavailable for next week's opening November Test against South Africa.

Healy is out for between four and five months – late January or sometime in February based on his rehabilitation rate – after tearing a hamstring off the bone. Moore will be sidelined for 12 weeks following shoulder surgery, while Cronin saw a specialist and has been diagnosed with a moderate ankle injury that will keep him out of action for a six-week period.

Official line

The fitness of

Mike Ross

is now the single most important issue in the build-up to next Saturday’s game against the Springboks.

The 41-times capped tighthead prop missed Leinster's two European Rugby Champions Cup matches against Wasps and Castres because of a groin strain but on Wednesday the official line coming from the Ireland camp was that he would train fully next week.

That’s not the first time such a statement has been heard, although it was previously offered in a Leinster context.

Schmidt might be tempted to cocoon Ross as much as he dares in a training scenario, allowing for the fact that he hasn’t played for some time.

If Ross were to suffer a setback, Schmidt would be left with a choice of four props who between them have started only one Test match from a total caps tally of 12.

Ulster's Declan Fitzpatrick is the most 'experienced' of the four having played a full Test match on his debut against New Zealand on the summer tour in 2012.

He turned in a decent performance in the 55 minutes he was on the pitch and subsequently won six caps, the last of which was in the November Test series last year against the All Blacks.

In April he suffered an irregular heartbeat and was hospitalised after a game for Ulster against the Glasgow Warriors in Scotstoun. He didn't require surgery and was allowed to resume his career.

Couple of concussions

Fitzpatrick has been unfortunate, picking up a couple of concussions that curtailed his game time, while he had to endure a one-game ban after being sent off for punching in a Guinness Pro12 fixture earlier this month .

Munster's Stephen Archer has won two caps as a replacement, the most recent being against Australia in November 2013. He spent the final couple of months of last season rehabbing a bulging disc in his neck.

Michael Bent arrived from New Zealand on a Leinster contract but before he had a chance to play for the province he was drafted into the Ireland squad – he qualifies through an Irish grandmother – and came on as a replacement against South Africa and Argentina, replacing Ross in the 2012 November Test series.

He’s deputised for the Corkman at tighthead in both of Leinster’s recent European Rugby Champions Cup matches.

The final contender is New Zealand-born, Connacht tighthead Rodney Ah You, who made his Ireland debut when coming on as a replacement during a summer Test against Argentina. He's spent most of this season behind White in the pecking order in Connacht.

Outstanding

Schmidt might draw some comfort – it’s a relative thing in the circumstances – from the fact that he has two outstanding young props available on the loosehead side of the scrum. McGrath and Munster’s

Dave Kilcoyne

boast remarkably similar statistics.

They are both 25 years old, have each won 10 caps for Ireland, and two apiece have been from the start of a Test match. It’ll be interesting to note if there are late withdrawals from Guinness Pro12 matches. Bent and Ah You are due to start tonight’s matches in the RDS and the Liberty stadium respectively.

The fact that Ireland play two of the biggest scrummaging sides in world rugby in the Springboks and Georgia – Australia are much improved – merely underlines the difficult task facing the squad over the next three weeks.