And for a Swansea man to skipper Wales in Cardiff's new stadium opens up the possibility his big day could be ruined by terrace abuse.
However, defender Williams - Wales' new footballer of the year - hopes support for the national cause will outweigh local rivalries.
Unfortunately, Williams' rise to national captain comes at the end of a week that saw Swansea beat their bitter local rivals in a Championship derby, with Williams making some critical remarks about the Bluebirds' style of play.
But he says: "This is a Wales game, it is not a Swansea or Cardiff game and we are playing at Cardiff which I hope will become our 'home' ground in the future.
"I just want the crowd to get behind the boys and help us to a win. We all play for different teams, the banter is good but we are playing for Wales and that is all that matters.
"This will be the biggest game of my career so far, even if it only a friendly. It is against a home nation and that makes it special."
He added: "I have not even thought about the fact that I'm a Swansea player captaining Wales in Cardiff. It is not an issue, we are all playing for Wales, that is all that matters.
"Whoever the captain is should not be an issue really. I know I was born in England, but my mum and her family are all Welsh and I feel Welsh.
"I am living in Wales now and that gives you the chance to really get a feel for it and understand what the fans want.
"I am learning the anthem and trying to sing it every time, I hope that shows my commitment and how seriously I am taking all this."
Boss John Toshack, a man who played for both clubs, gives short shrift to the Cardiff-Swansea debate.
He said: "It doesn't matter whether we were playing in Swansea, Glasgow or anywhere, at this moment I believe Ashley is the man to be captain.
"Ashley is the right choice, and it is nothing to do with where we are playing. It is something I have not even thought about.
"We have had to select a third captain in three games because of injuries, and the form he is in makes it the right decision.
"He is on top of his game, he has had a good week. He won the derby against Cardiff, he picked up our footballer of the year award in midweek and now he has got the captaincy of Wales.
"We hope it goes well for him. I don't think Joe Ledley will have a problem with this, despite him having been skipper himself recently and this will be his home ground.
"It's a bit late to change the venue now because there's a Swansea man I want as skipper!"
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