Joey Carbery has admitted fearing for his World Cup when he damaged ankle ligaments in Ireland's warm-up win over Italy.
The 23-year-old has pulled off a remarkable recovery to turn from a major tournament doubt to proving his fitness for Sunday's Pool A opener against Scotland in Yokohama.
Carbery believes he has been lucky to fight back to full health so quickly, having hobbled out of Ireland's 29-10 victory over Italy in Dublin on August 10.
Less than six weeks later the Munster playmaker has not just made his first World Cup, he has done so ready to take part from the off.
Asked if he had feared his World Cup was over after that ankle injury, Carbery said: "In the back of your mind you do think that but I suppose I was very fortunate in being able to get back as quickly as I did.
"Within myself I was thinking 'will I be ready, will I be OK to go?', but then I had great help with the physios and the doctor who got me through it all.
"It was a lot of long days, but it's worth it all in the end. It's great to be back training, the ankle's feeling pretty good.
"There were a couple of nervous days after the injury happened, so I'm just happy to be here.
"I suppose it's great the ankle has healed, and I'm pretty happy with it all. I'm feeling pretty good in training, so it's positive."
Carbery will now be pushing for as much match action at his preferred fly-half role as possible, but the former Leinster pivot will also act as Ireland's third option at number nine.
Head coach Joe Schmidt selected just Conor Murray and Luke McGrath as his recognised scrum-halves in the World Cup 31, leaving Carbery offering a third option.
The New Zealand-born playmaker has not tasted competitive action at nine since his school days, but insists he is comfortable wherever he is deployed.
"Under-18s was the last time I played scrum-half," said Carbery.
"Then I moved to 10 and went to full-back probably a year later.
"I've only trained this week so I've only been around 10, hopefully over the next couple of weeks I'll get in at a few other positions, but so far it's only 10.
"I don't mind being versatile, I suppose it adds another string to my bow. Wherever the management need me I'll fit in."