JAMIE Roberts has warned his Wales teammates that Argentina will show them no mercy if they don’t learn from Saturday’s thrashing by Australia.

The 84-cap centre admitted the Wallabies gave Rob Howley’s men a “kick up the backside” as the visitors cruised to a 32-8 victory at the Principality Stadium.

It was Wales’ 12th consecutive defeat to Australia, a run stretching back to 2008, and their fifth Test loss on the bounce.

After the game, Roberts admitted he was finding hard to explain why Wales were so poor in their opening match of the autumn series.

But he does know that if they deliver anything like their weekend performance against the Pumas this Saturday then a similar outcome will be the result.

“We’ve got to learn from it,” he said. “I think the main thing to learn from this is to slow their speed of ball.

“Australia pride themselves on the speed of ball at the ruck, we spoke about that in the week, and they carried well.

“They got the speed of ball and that doesn’t allow you to reset in defence, and they caused us some problems.

“That’s something we need to address and it doesn’t get any easier, Argentina are a formidable outfit this year and they’ve improved a lot the last few years.”

He continued: “I watched Argentina play Australia at Twickenham a few weeks back and they’ll play.

“They’ll play from their own half and they have big carriers and are a physical side, and what we didn’t do today we have to next week, and that’s stop their momentum.

“It will be a long day at the office if we don’t.”

Commenting further on the challenge Argentina will provide, he added: “Rugby is about momentum, it’s about speed of ball, and we just didn’t win that battle against Australia, and they played some good stuff in attack and caused us problems, along with some poor defensive reads from us.

“Argentina will pose a similar threat with a lot of pace out wide, and if we allow them momentum, speed of ball and space in the game it will be another tough day.”

The only real highlight for Wales at the weekend was Roberts’ centre partner Scott Williams’ second-half try.

Wings Alex Cuthbert and Hallam Amos also went close to scoring as well but Australia’s first-half dominance had already taken the game away from the hosts by that stage.

“It’s certainly a kick up the backside for us and we go into training on Monday and we have to address the issues,” said Roberts.