Williams has been absent with an ankle problem for the previous four matches, but Rangel believes that the Welsh international will return against Sunderland on October 19.
The 30-year-old told South Wales Evening Post: "Ash has not really trained with the team. He's been having treatment.
"Obviously, he will be fit when we come back. How many Premier League games did he play in a row without a rest?
"Ash has not had many injuries. Hopefully he will be back to full fitness, get back in the team and help us."
Williams has withdrawn from the Wales squad to concentrate on his recovery from injury.