Cronin injury starts race to be second to Best - Here are five candidates for the Irish bench
Competition is heating up to claim back-up spot to Ireland captain ahead of Six Nations campaign
Irish rugby is in a good place as the Six Nations begins to loom into view but there are still a few positions where options are thin on the ground for Joe Schmidt.
The health of Conor Murray, Johnny Sexton, Tadhg Furlong and Devin Toner are all crucial to the national team's progress in the coming month, but perhaps the man the coach can ill-afford to lose most is his captain Rory Best.
The sight of Seán Cronin limping off the RDS pitch on Friday night only underlined the skipper's importance.
With Ireland's primary impact replacement expected to be ruled out for the majority of the campaign in the coming days after he tore his hamstring against Zebre, the door has opened for another to step forward. Unfortunately, there are not a lot of experienced options out there.
There is a reason why three of the project players imported into the Irish system have been hookers.
For some reason, the country that produced Keith Wood is struggling to produce No 2s of the requisite standard for international rugby, meaning the IRFU have looked beyond the borders for candidates.
It is a testament to the endurance of Best that Schmidt has capped only six hookers during his four seasons in charge, two of whom came through the South African system.
Three of those have earned one cap each - one of which in Rob Herring's case came on the flank against Argentina in 2014. Damien Varley has retired, while James Tracy made his debut in November and otherwise it has been Best backed up by either Cronin or Richardt Strauss.
Since last year's World Cup, the hierarchy has been clear-cut given Strauss's injury problems with Best and Cronin the clear first and second choices.
Now, Best remains in situ but the battle to back him up is under way.
A try-scorer on his Ireland debut against Canada in November, the Leinster hooker could be the player who benefits most from Cronin's absence at provincial level.
Highly rated by the management at both Leinster and Ireland as a result of his size, strength and capacity in the ruck and tackle, the 25-year-old Kildare native is a converted prop who has been covering for the Limerick man throughout this season.
Perhaps as a result of his late adoption of the position, his throwing has not always been on the money but as third choice during the autumn internationals he comes into the spring as the incumbent.
The man who won the battle to back Best up during the World Cup is available and has trust in the bank as a result of his previous performances under Schmidt.
An aggressive carrier and ruck specialist who is accurate out of touch and has plenty of experience, Strauss is the original project player and has never let his adopted country down.
Fit again after a nightmare year, the Bloemfontein native could even dislodge Tracy at Leinster if Leo Cullen wants to go with experience in the coming fortnight and given the Ireland coach's predilection for players who have been there and done it before for him, he could well come up on the outside and regain the No 16 shirt.
Perhaps the break-out star of the Munster revival, the clamour for international recognition for the ever-improving Cork man is growing and has plenty of merit.
A former Ireland U-20 captain, the 24-year-old is thriving under the tutelage of Jerry Flannery and is holding off the challenge of highly-rated new signing Rhys Marshall who is the latest project recruit in the Irish system.
Scannell has yet to be involved in an Ireland camp and that may work to his disadvantage given the level of detail needed to get up to speed at Carton House.
Yet, he has emerged as a leader in the Munster ranks and if the Six Nations call doesn't come then the summer tour should see him take the next step if injuries go his way.
Arguably the form pick, it would be harsh to leave him out of the Championship panel.
The Ulster vice-captain's main impediment to selection is the presence of Best at Ulster and, while the Cape Town native is a consistent performer and recognised leader at provincial level, he doesn't start games when the Ireland skipper is fit.
Qualifies to play for Ireland by birth and made his debut as a replacement flanker against Argentina in Tucuman in 2014, but hasn't been able to add to that appearance despite taking part in plenty of camp sessions.
Last involved in the squad during last year's Six Nations, he appears to have been passed out by Tracy but has a good knowledge of the systems that could stand to him.
He's a good set-piece operator with a strong defensive game and an ability to carry, but he needs a run of games to turn heads and with Ulster out of form and facing a European exit he may have to rely on another injury to get in.
The Mayo man is enjoying an impressive season for Connacht and is starting to come into contention for the international squad, even if the summer tour offers perhaps the more realistic opening.
Like Herring, he faces an unenviable challenge to wrest the provincial jersey off an experienced leadership figure in Tom McCartney who becomes Irish-qualified in November and is likely to leapfrog everyone on this list when he does.
The New Zealander is an excellent player, but his deputy is growing more able by the season and is enjoying a fine campaign.His throwing has improved but it his ball-carrying that perhaps earns the most attention.
Although Connacht have struggled for form this season, he has been one of the shining lights. He is likely to have to bide his time, but international recognition may not be far away.