Ireland's defeat by Japan has thrust Joe Schmidt's men into knockout rugby a week early at the World Cup, admits Iain Henderson.

Head coach Schmidt's side must see off Samoa in Fukuoka on Saturday to reach the last eight, with their shock 19-12 loss to Japan turning the final Pool A clash into an unforeseen eliminator.

Forwards coach Simon Easterby relished an extra edge in training on Tuesday, with Ulster lock Henderson insisting Ireland have cranked up preparations this week.

"The knockouts have started a week earlier than we would have liked, and that's upped the intensity, across training and meetings," said Henderson.

"You see everyone putting in a bit of extra time, be it in video analysis or a bit of extra time in the gym before we hit the pitch, just to make sure everybody is as right and as nailed-on as possible for the weekend.

"You can feel that all having built throughout the weeks. All we can hope for now is that it comes to fruition over the weekend."

Tournament hosts Japan edged towards a first-ever World Cup quarter-final by sneaking a last-gasp bonus point in their 38-19 win over Samoa.

Lions lock Henderson insisted that Samoa's determination to play out from their own 22 might have cost them that fourth try against Japan - but leaves them a very dangerous proposition this weekend.

"We saw Samoa try to play right at the death and then Japan ended up getting the bonus point," said Henderson.

"That gives you an idea of what Samoa are trying to do: they're looking to play from anywhere at any time and that's something we have to be fully aware of.

"They're going to be ultra-excited to get the ball in their hand, they're going to be looking to do as much damage to us as possible.

"If you look at the way Japan started against us, I think that's a good indication of what Samoa are going to try and do.

"We know, we've reviewed quite a few of their players already and we know in their pack and their whole backline there are threats all over the pitch.

"We have to be very wary of that and not try to do anything out of the ordinary for us." 

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Follow Ireland v Samoa on Saturday 12 October (kick-off 11.45am) via the live blog on RTÉ.ie/Sport and the News Now App, watch live on RTÉ2 or listen to live match commentary on RTÉ 2fm.