Welsh superstar Gareth Bale, who scored a double in the 2-1 Group A win over the Scots in Cardiff in October, travelled to Glasgow separately from the rest of the squad after missing training all week with a virus.
The Tottenham forward had a truncated training session at a freezing national stadium last night after manager Chris Coleman insisted he had a "a very good chance" of playing in the face of numerous questions about the player at the pre-match press conference.
Williams was also quizzed about Bale and while acknowledging his quality, reminded the Scots that there will be other threats.
The Swansea defender said: "He has had a virus that he caught from his daughter, and had an ankle knock as well, and we hadn't seen him for a few days but he is here and he should be playing, all being well.
"He is everything to us, a world-class player in great form, we are pleased to have him and I think we are a different team with him.
"But we have a lot of other good players in the team, it isn't just Gareth Bale although, as I said, I think he is world-class player.
"If I was playing against Wales I would pay him close attention but you can't forget the other boys, there is Craig Bellamy who is a top-class player as well.
"I think we have other weapons as well and hopefully we can show that we are a good team tonight."
Williams arrived in Scotland with a Capital One League Cup winners' medal following a 5-0 victory over Bradford City at Wembley last month.
He was still basking in the glory of Wales' record 30-3 rugby union win over England at the Millennium Stadium at the weekend which clinched the RBS Six Nations title.
With a nod to Cardiff City's lofty position at the top of the npower Championship, Williams looked forward to riding the crest of the sporting wave into the match against the Scots.
"I was thinking about that the other night when I was watching a replay of the rugby game," he said.
"Everyone is still buzzing, rugby is a massive sport in Wales and it was a great day for everyone concerned.
"I thought it would be nice if we could get a win as well and keep the momentum going in Wales and give the public something to cheer about again.
"Swansea have had a good season, Cardiff are top of the league so it would be nice if we could carry that on and that is what we will be looking to do tomorrow night.
"Playing against Scotland gives it a little extra as well being a home nations game and both countries will be desperate to win."