Williams was at fault with Benteke's goal which completed a nightmare week for the skipper after being part of the Wales team beaten 6-1 by Serbia.
Swans boss Michael Laudrup said: "Ashley is a super guy but he has had a very severe week.
"When you lose a club game, you always have the next one to recover. But when it is an international, at the start of a World Cup campaign, and you lose two games and one result is very savage, it hurts.
"Then four or days later you have to play a tough away game. I think he did well. Of course, it was a mistake at the end but, whether it was one-nil or two-nil, doesn't make a big difference.
"I said to him afterwards to now go and relax and I am sure knowing him he will come back after a couple of days with his family and have a huge game against Everton."