Scott Williams in full flight for Wales © Getty Images

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It was the eleventh minute of Ireland's match against Wales during the 2014 Six Nations when Brian O'Driscoll, closing in on a world-record 141 Test caps, felt the tackle that he feared would end his life.

The clock was just ticking into the twelfth when the men in green had a lineout about 35 metres from the Welsh line. It was a move straight off the training paddock.

Rory Best found Peter O'Mahony in the second pod who flung the ball to Conor Murray. Like day into night, Murray passed right to Jonathan Sexton, who hit a miss pass to O'Driscoll.

Rob Kearney was making the darting run off O'Driscoll's right shoulder but the pass never found him. Instead, Scott Williams flew out of the Welsh line and hit O'Driscoll with such ferocity he was left prone on the floor while the Welsh centre held his shoulder. Irish supporters held their collective breath while O'Driscoll searched for his.

In O'Driscoll's recent autobiography The Test he gives a stark account of the tackle. "He [Williams] reads the play and comes up like a train ... I'm at my weakest, Williams at his strongest. He absolutely ends me.

"He catches me full square in the sternum with his right shoulder. It's the biggest collision of my career, by far - 27 g [-force] on the GPS unit ... As I hit the floor every last ounce of breath has gone from my body. I've been badly winded before, but nothing like this.

"I'm barely aware of any pain but it feels like the closest thing to dying - unable to breathe, panicking."

After checking his ribs were in the right order, O'Driscoll stands and looks for Williams "to send him my compliments on an unbelievable shot".

Scoring that try for Wales against England © Getty Images

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"I do analysis before a game on the opposition and try to look at their set-ups," Williams tells ESPN. "I recognised one of their set-ups and knew what they were going to do.

"I spoke to George [North] and told him I was going to try and make a spot tackle on O'Driscoll as he was going to get the ball through the middle of the wing. I managed to get him man and ball and he saw me coming last minute.

"My shoulder hit him on the arm and my initial reaction was pain in my shoulder and I tried carrying on for a bit but knew something was wrong. I had a couple of injuries before but this was different.

"The pain was severe but I only realised when I took my jersey off that I had injured my A/C joint. But no regrets, that's rugby."

It was the tackle that ended Williams' campaign.

He was forced to have surgery and although there were hopes he would make Wales' end-of-season tour to South Africa, he opted to rest. "I had torn my deltoid in the tackle and during the rehab I irritated it a little bit and that set me back a week or two," he says.

"After speaking to the physios they decided it was the best option I forgot about the season and got a full pre-season as obviously this is a big year. It was a sensible decision, the right one."

When Williams made his regional debut for the Scarlets against the Ospreys in 2010, he was billed as a promising youngster.

Test selection was expected to be put on hold for a few years, in part due to the wealth of talent Wales have in that area but also because young centres sometimes endure tough starts to their international career and it takes them years to recover from it. Just ask Mathew Tait.

But life did not move slowly for Williams. Instead, he was fast-tracked into Wales' 2011 World Cup squad. The following year he was the toast of the country when he scored the winning try against England, tearing the ball from Courtney Lawes' grasp and running under the Twickenham posts on the way to Wales' grand slam.

"Everything happened so quickly," Williams says. "I was lucky to get the opportunity to go on the training camp to the World Cup. Playing for Wales was all I wanted to do as a kid.

"I remember Scott Gibbs' [1999] try against England and I always wanted to do something like that; luckily enough I managed to do that in 2012. Beating England and scoring was a personal highlight but it was a team performance, it's not something I just want to be remembered for."

Williams, with 25 caps to his name, is now expected to play an important role for Wales in the forthcoming autumn internationals and next year's World Cup.

Come November, Wales will be searching for blood. Far too often they have fallen at the final hurdle to the southern hemisphere's finest. Clasping defeat from the jaws of victory has become a frequent occurrence.

"We are due a win, there's not a better time in terms of timing ahead of the World Cup," is Williams' bullish retort. "This is our time to get a southern hemisphere scalp."

But before Wales and thoughts of Millennium Stadium glory come the Scarlets. It is testament to Williams' stock and reputation in the game that at 24-years-old he was named vice-captain for the Scarlets this term. Injury to Ken Owens saw him lead the Scarlets out against Toulon at the weekend.

© Getty Images

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He admits taking on the captaincy has seen him move "out of his comfort zone" but is keen to "lead by example" and keep talking to a minimum. It's the Sam Warburton mould of captaincy. "He doesn't say much but he's the ultimate pro and leads by example on and off the field," Williams says of his Wales skipper. "That is why he's been such a successful captain"

Any doubts over the state of Williams' shoulder were put to bed against Toulon last weekend. He was charged with the unenviable task of keeping bulldozing centre Mathieu Bastareaud at bay. But it is these sorts of occasions that Williams relishes.

"I enjoyed it," he says. "I was blowing at times but it goes to show European level is a massive step up from the PRO12. Personally it was good to play against some of the best players in the world and that's where you measure yourself. I was glad to come out injury free.

"We were gutted not to come away with something, we gave it a good shot but it was a couple of errors that let us down. For us to go out there against the champions and surprise them a little bit hopefully changed some people's opinions. We have a lot more to show.

"But we need to forget about Toulon and focus on Leicester. It'll be a tough game. I think they have been disappointed with a few of their results but they put in a good performance against Ulster. It's a must-win for us."

In 12 months time, Williams could have played in two World Cups by the age of 25. He does not want his legacy to just be that try against England in 2012 or that tackle on O'Driscoll - and it would take a brave man to stand in his way as he fights to achieve his goal.