British and Irish Lions number eight Taulupe Faletau has been ruled out of the World Cup with a collarbone injury.

Williams says Wales are still in good shape at number eight as long as Ross Moriarty stays fit.

"It is a huge blow but Wales have managed without Faletau over the last 18 months," Williams said.

"Ross Moriarty was sensational playing number eight during the Six Nations and the Grand Slam, and obviously we had a clean-sweep in the autumn as well when Faletau was injured.

"What it does is put huge pressure now and everyone with their fingers crossed that nobody else gets injured in that back-row.

"Particularly Moriarty because he's the only specialist number eight, although maybe Josh Navidi is the other guy who could do a job at eight."

Faletau has played 72 times for Wales since making his debut against the Barbarians in 2011 and has also played four Tests for the Lions across two tours.

But the Bath player has not played in a Test since March 2018 and fractured his right forearm in October 2018.

He re-broke the same arm last January and had been on his way back from that injury before suffering the latest setback during Wales training.

"Faletau is a world-class player, he's proven for Wales how valuable he's been since he made his debut back in 2011," Williams added.

"You feel personally for him as well, because he would have worked hard to get back after such a difficult injury as his broken arm."

Wales play two Tests against England - the first at Twickenham on 11 August - and two against Ireland before their World Cup starts against Georgia on 23 September.

Williams admits there is a risk that more injuries could occur during those warm-ups, but says the Wales players must go into the World Cup with tough games already under their belts.

"In some ways they're a necessary evil, you cannot have no competitive rugby if you're a northern hemisphere player and your season finished in May," said Williams, who won 100 Wales caps and played in three World Cups.

"I know a lot of people are questioning why they have four such tough games, but the players are not going to play in every one.

"It's a difficult balancing act, you don't want to lose any key players but you're just as likely to get injured in training."