Title charge in jeopardy as injuries to key pair threaten to derail Irish Grand Slam ambitions
If you were to ask Joe Schmidt to draw up a list of players he could least afford to lose to injury while still sustaining a tilt at the Six Nations title, Tadhg Furlong and Robbie Henshaw's names would be high up.
For the Ireland coach, the loss of two pivotal members of his side is a major problem ahead of the games to come.
Neither player has officially been ruled out of the tournament, but both seem unlikely to feature against Wales on Saturday week. For Henshaw, the prognosis looks likely to be more serious.
There has been a lot of talk about depth since Ireland handed out a ream of new caps in June and November, but there are still certain individuals who the team rely on.
Conor Murray and Johnny Sexton are still pre-eminent in their positions, while Henshaw is a key defensive leader. Furlong is the only Ireland starter who could accurately claim to be the best player in the world in his position.
In other departments cover exists for the front-liners, but in midfield and on the tighthead side of the scrum the resources remain callow.
Losing Henshaw opens the door for Chris Farrell, who deputised well in November when the Athlone native was out with a hamstring issue, but this is a further step up for the Fermanagh man.
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Replacing Furlong is an even trickier business. Andrew Porter was outstanding against Italy on Saturday, but while he offers a brilliant work-rate around the park he is still learning his trade at scrum-time after switching sides last season.
Before his 77-minute run-out at the top level on Saturday, the 22-year-old had only started three senior games at tighthead for Leinster, all of which came in the Guinness PRO14.
Schmidt also has John Ryan to call on and, at 29, the Munster man is a more experienced campaigner. However, he has been second choice for his province in all of their biggest games this season and struggled when introduced in Paris on the opening weekend.
While Porter contributed so much around the park on Saturday, making 13 carries for 18 metres and seven tackles, while also holding up the scrum and making an impact at the breakdown, he still has a way to go in terms of matching Furlong's experience.
Schmidt has clearly earmarked the St Andrew's graduate for a role in the seasons to come, but he was hoping to gradually build his experience rather than throw him directly in against the big dogs in the white heat of Six Nations battle.
Of course there remains a chance that Furlong's injury is not as bad as it looked. He pulled his left hamstring as he decelerated after chasing centre Tommaso Boni in the fourth minute of the game and will go for scans before an update is issued in the coming days.
Henshaw, meanwhile, looked to have suffered a serious shoulder injury in scoring his second try of the afternoon after 44 minutes.
Referee Romain Poite described it as a "bad injury" when calling for attention, while the player needed acute pain relief as he received treatment before being replaced by Jordan Larmour.
If Garry Ringrose was fit and available the loss of Henshaw would be softened, but his Leinster team-mate is also on the recovery trail after an ankle operation and is unlikely to make it back for this week's clash with the Scarlets at the RDS.
He may be fit to face Wales, but Schmidt expressed concern about throwing him straight in for his first cap since June.
The coach will be acutely aware that Ringrose was struggling for form having missed the start of the season with a shoulder problem and, in an ideal world, he would get a run of games with Leinster before coming back to the highest level.
Therefore it would seem likely that Farrell will step back in.
The Ulster-born Munster centre offers similar physical attributes to his Leinster rival, while he has the advantage of having been in camp for the first two weeks of the campaign.
Schmidt must make a decision on whether to release him to play for his province this weekend or keep him in camp in Athlone to build up his time alongside Bundee Aki.
Having suffered a knee injury in the Argentina game, Farrell returned for three games in January, but rather than playing against Zebre on Saturday he was kept in Dublin to train with the senior team.
With nine points from their first two games and with Wales and Scotland up next at home, Ireland are in a strong position to go to their final game in Twickenham with the title on the line. However, the injury toll from Saturday threatens to undermine that momentum.
"You do feel that you've a chance when you can get those two wins and especially an away win first up," Schmidt, who chose not to hold a briefing with the written press for the first time in his 52 Tests with Ireland, said.
"You know that your next two games are at home, we haven't lost a home Six Nations game in the five years that I've been involved in, so there's a real benchmark and pride that we can hopefully defend.
"We probably had a couple of knockbacks injury-wise today, hopefully most of them are going to be okay, so it's a bit of a wait and see. Every week is a little bit different and every championship is a little bit different."