Ireland don't need to look too far past what happened in the last World Cup to brace themselves for Japan, according to Jordi Murphy.
Four years ago in Brighton the Brave Blossoms pulled off the biggest World Cup upset of all when they came from behind to record a 34-32 victory over two-time winners South Africa.
Murphy, who missed out on selection for this year’s competition but remains on standby, was with the Ireland team four years ago when Japan, then under current England coach Eddie Jones, shocked the Springboks.
"We only need to look back at the last World Cup," Murphy told the RTÉ Rugby podcast.
"I was actually with the whole squad in the team room watching that historic show against South Africa.
"It was just incredible. Before the game if someone had told you that Japan are going to beat South Africa today you would have laughed at them.
"That’s the potential banana skin that they are. It’s not like that was a one-time thing, they’ve been putting in performances month after month for the last couple of years.
"They are the tournament hosts and they are going to have incredible support behind them and they are going to be seriously buzzed up.
"I wouldn’t be thinking too much into what team they might play.
"If you were in their camp you might even be thinking, 'if we beat Ireland there is no reason that we can’t go and top the group’ and if they were able to do that in a home World Cup that would be incredible.
"They’ve made history before and I’m sure they’ll want to do it again."
Follow Ireland v Japan on Saturday (kick-off 8.15am) via the live blog on RTÉ.ie/Sport and the News Now App, watch live on RTÉ2 from 7.30am or listen to live match commentary on RTÉ Radio 1.