Back row forward Caelan Doris says Ireland's attack has the ability to "cause damage" to South Africa on Saturday providing the forward pack can physically match the World Champions.

"If we can match them in terms of physicality we have a lot of belief in our attack," said Doris, 25.

The number eight has been outstanding for Ireland over the past two seasons.

His ability to carry possession - in addition to his breakdown work - is likely to be a key factor for Ireland at the Stade de France but he knows that Andy Farrell's side face a huge physical challenge against the defending champions.

'The sheer size of them'

"I remember the sheer size of them, playing them in November, their physicality, but it's certainly not the only string to their bow," added the Leinster star.

"They have a lot of pace in their backs - their forwards are capable of keeping the ball alive and offloading.

"Obviously the physicality is tied into their set-piece. They've got a great maul, great line-out options and a strong scrum as well.

"Getting those areas right is going to be big. Our collisions, something we've spoken about over the last few weeks, [are] something we haven't been happy with going back to the warm-up games, even though they have improved over the last couple of weeks."

Doris is fully mindful that this weekend's contest is going to be a huge "step up" from the opening facile wins over Romania and Tonga.

"Things like two-man tackles, getting our tackle line right, our tackle entry, all those things are going to be pretty big this weekend.

"Some of the threats they have out wide with their backs. Their forwards and their ability to keep the ball alive after having won dominant collisions.

"Going hard at the breakdown is something we've seen from them over the last while too and we reckon they'll try and disrupt there too quite a bit too."

But while Ireland will face their first genuine test of this World Cup, Doris insists that there is a "special feeling to the week".

"We know we have to deliver our best and what comes with that is maybe little extra conversations or an extra walk through in the evening, a bit of extra video, extra visualisation, just to make sure you're fully across the board.

"The lads are in optimal condition, as good as we have seen over the last few years. We'd back our fitness against most teams.

"There's a belief we can improve, it's always striving for the perfect performance."