Harry Redknapp's side may include several new faces after Tal Ben Haim, Loic Remy, Yun Suk-young, Christopher Samba, Andros Townsend and Jermaine Jenas joined in the January transfer window.
That has left Michael Laudrup's Swans in the dark over Rangers' systems, but Williams is sure the visitors will still pose a genuine threat - despite being rock-bottom of the Premier League.
"With a new manager and a team made up of a lot of new players, you don't really know what's going to happen. That's a fact," said the Wales captain.
"We went out and won that game against them on the opening day and that gave us a lot of confidence. But that was such a strange day and a lot has happened since then.
"Having said that, we feel like we can win most games these days, especially at home. We lost last Saturday at West Ham so we want to get back on track this week."
Laudrup's men have the Capital One Cup final to look forward to on February 24 - but Williams is focused on league matters until then and is urging his team-mates to do likewise.
The centre-back added: "We're in a cup final, we're doing really well and we didn't think that would happen back in August. That's football and it's credit to everyone who has worked hard this season.
"But we need results from these next two games against QPR and Liverpool, then we get confidence going into the cup final.
"We want to continue performing well to keep our good form going. It's not just about the cup final, we've got points to play for."