Alex Cuthbert defends yellow card for deliberate knock on against Australia

The winger has struggled for form in the last 18 months, and had been heavily criticised for his performances in the Rugby World Cup.

Going for an interception with less than 10 minutes to go, he spiked the ball and referee Craig Joubert gave him his marching orders.

"I guess I got there quicker than I thought and I tried to go for it," he said.

"It looked worse than it was I think because I was in front of Folau I think it was but I didn't quite get the two hands to it or the one hand motioning up.

"It looks like it was going down so I guess it was a fair yellow, but they had an advantage anyway so I went for it and they would've scored maybe if I didn't intervene."

It's been a frustrating time for the Cardiff Blue, and he has not been helped by some pretty questionable service to his wing.

He said: "Obviously as a winger, you want to get the ball as much as you can.

"I feel like I'm putting myself in the situations, but obviously that extra pass or that little bit of communication between the boys means it's just not working out.

"I thought we played well in parts, especially when they were down to 13 men, but they defended their hearts out on the line and deserved the win.

"Any other game we might have got a penalty try or our scrum would've gone over and Toby [Faletau] would've scored.

"It's just another close encounter and we've come out second best.

"We had so many chances in their 22 when they were down to 13, I think we should've scored from that.

"But we've got to think we got out of a group nobody thought we'd get out of and we're against a team now in the quarter final where the last time we played them, we beat them."

Cuthbert conceded the period Australia went down to 13 men was where Wales lost the game.

"I think maybe we were unlucky," he said.  

"We had a couple held up over the line and maybe on another day they'd have been given as well as a penalty try.

"I thought we were pretty dominant close to their tryline as well, and especially with the yellow cards as well.

"But we just didn't show that clinical edge that we've shown in the past and in test match rugby like this you just have to take those chances.

"Especially in the World Cup.

"We knew we were through but we really wanted that win to top the group."

The makeshift backline didn't function and the George North experiment in the centre did not pay off and he has been switched back to the flank against South Africa.

Cuthbert said: "We trained really well as a team and George has filled in and played centre plenty of times.

"I thought he had a good game and I thought Gareth [Anscombe] came in and played really well and looked to get involved a lot.

"It was just one of those days where it didn't click.

"We had all that possession and didn't make the most of it."

As much as Cuthbert's attacking game has faltered, his defensive play has improved no-end under Shaun Edwards' watch.

He was involved in two choke tackles and two defensive reads in the first half, something he would have struggled with at the start of his career.

"With Shaun we work on a lot of linespeed and for us not to allow Australia to score a try is quite an achievement with the team they have," he said.

"We wanted to nullify them as much as possible, and I thought we did that.

"When you're in that white zone as we call it in the 22, you have to come away with points and we didn't do that."

Despite the loss, Wales will not fear the South Africans in the quarter final having beaten them last time out in the autumn international.

Cuthbert said: "We should've beaten them twice at their place and managed to beat them in the Autumn.

"It's knockout rugby. It's what every professional player wants to be involved in.

"For us it's about getting our game how we want it.

"We know it's going to be a tough, physical game and we won that battle [Australia] in some sense.

"It's only small margins, but that's test rugby."