Joey Carbery's injury setback leaves Ireland with a fly-half dilemma
That Joey Carbery is due to be fit in time for the World Cup opener against Scotland is good news for Joe Schmidt and his team, but the ankle injury suffered by the 23-year-old Munster out-half will prove disruptive to the head coach's plans for the next month.
Ireland travel to Portugal for their warm-weather training camp tomorrow, before facing England, Wales and Wales again in successive weekends before flying to Japan.
And while Carbery is likely to remain with the team to partake in their build-up to the tournament, it looks unlikely that he'll see any game-time until that first World Cup fixture.
Schmidt is engaged in a delicate balancing act between protecting his leading lights from injury and arriving in Yokohama for that first game ready to hit the ground running with momentum behind them.
The Six Nations put a dent in the team's confidence and they'll want to avoid further damage in their next two games at Twickenham and Cardiff when facing tough, physical opposition.
So, Schmidt must ponder what role Johnny Sexton will play in the coming fortnight and whether he needs to get Jack Carty a start in a major international venue before he goes to Japan.
He must figure out whether Byrne has a role to play in the coming weeks, while he must also be considering who will be next cab off the rank in case of emergency, with Bristol-based Ian Madigan the most obvious candidate.
Schmidt may look at the England and Wales away games as a dry run for the pool clashes against Scotland and Japan, meaning Sexton could be slated to start both games alongside Conor Murray in a close-to-full-strength side.
This would allow him to wrap his stars in cotton wool for the final farewell game against the Welsh, which is just a week before they make the long trip east.
Warren Gatland last week admitted that he has spoken to Schmidt about their selection strategy for those games and it would be no surprise to hear that similar conversations have taken place between the Ireland coach and Eddie Jones.
As the team's talisman, Sexton's presence on the plane is essential to Ireland's success and the nation will be crossing its fingers when he takes the field in the coming weeks.
Whereas Schmidt might have rotated him with Carbery, he may be more reluctant to hand Carty or Byrne their first international starts in London or Wales against two of the main contenders for the Webb Ellis trophy.
At the same time, he might see it as the perfect opportunity to see what they're made of since there's every chance one or both of them could have to play a role in Japan.
Sexton will bristle at the idea that he might need protection from himself, but when he plays the out-half inevitably becomes a target for opposition runners and tacklers.
It seems almost certain that the coach will take three out-halves to Japan, while it looks increasingly likely that only two scrum-halves will go but there won't be a chance now to get Carbery a couple of minutes at No 9.
Schmidt might see the bright side, things could have been far, far worse if he'd lost Carbery for longer.
But he won't be happy that his plans for such an important position have already been disrupted to this extent and that he may be forced to lean on his main man more heavily than he would have liked.