Ireland will go into Friday's World Cup Super Eights match against defending champions Australia full of optimism despite losing their last four games, skipper Trent Johnston said.

World Cup debutants Ireland remain rooted at the bottom of the standings after their crushing 129-run defeat by New Zealand in Guyana on Monday.

However, having made New Zealand struggle on 83 for three and 189 for seven in their innings, Ireland feel they have the ability to rattle the big guns in the tournament -- even though the Kiwis recovered to take 59 runs from the last five overs to reach 263-8.

"It was disappointing but a lot of positives came out of the game," the Australian-born Johnston said. "You've got to take all the positives and take them forward.

"If you can't be up for a game against Australia you shouldn't be playing cricket. That's all the motivation the other 14 members of the squad need."

Ireland coach Adrian Birrell is hoping Bangladesh's shock 67-run victory over South Africa, ranked number one at the time, will inspire his team.

Johnston feels Ireland's high standard of fielding will also help them against Ricky Ponting's men.

"If we can execute the other two disciplines to the standards that we want we can probably get a bit closer to these teams," Johnston said.

"Bowling-wise we've had great starts up until New Zealand and we have got to close out the innings. These are things we are learning but it's professionals against amateurs. We will just go out there and do our vest best."

New Zealand skipper Stephen Fleming urged them to work on their consistency.

"They have got to play well for a longer period of time," Fleming said. "(Against us) their new-ball bowling was below probably where they would want it to be and their death bowling wasn't so effective.

"Their batting is going to be put under pressure so they've got to do some work there but the basics are there as is the youth of the side, and the captaincy will give them opportunities.

"It's just whether they can sustain pressure for a long enough period of time."