And the Bridgend prop - who will play as hooker for his country - has resolved to take his chance on his full international debut, despite the circumstances of his inclusion being less than ideal.
Williams has been given his chance after Jonathon Humphreys, Wales' captain for the Round 2 match against England, failed to recover from a shoulder injury from a shoulder injury he sustained during Baths' 30-9 Zurich Premiership victory over Saracens last weekend.
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Williams has made just two appearances for Wales, both as replacements, and has yet to end up on a winning side. And he knows on his full debut he must impress.
'I've got a chance and I've just got to take it,' he said.
'It's like a dream - I have gone from playing for my club to making Wales' starting line-up. But it will be very real tomorrow and I've got to go out and perform.
'I wasn't really expecting to start, especially as Humphs has come in and done such a great job, but he has picked up an injury, and I've got to go out and play now.'
And Williams is glad of the support Humphreys.
'Humphs has helped me a lot. I am still learning, and he has given me pointers with his experience,' said Williams.
'He's always talking to me and helping me, and it is great to be able to learn off someone like him.'
WILLIAMS WILL LEAD WALES