Argentina are holding out hope that captain Agustin Creevy can shake off a leg problem and be fit for Sunday's World Cup semi-final with Australia.

Hooker Creevy will undergo consultation on an as-yet unidentified leg issue on Monday, with the 30-year-old central to the Pumas' cause.

Julian Montoya replaced Creevy midway through the second half of Sunday's 43-20 quarter-final victory over Ireland at Cardiff's Millennium Stadium, and remains on stand-by to step in for the skipper.

The 21-year-old front-rower insisted he hopes his captain can fight back to fitness to start against the Wallabies, but is still ready for action if required.

"We're all very hopeful that Gus will be okay and that he can make it," said Montoya.

"He's the captain, he's an excellent player an excellent person, so he's very influential.

"In my place I want to do the best for the team, if I must be outside shouting for my team, taking on the water, that's what I will do. "But if I must enter the game, starting or not, I'll fight for the best for the team as well.

"I hope Gus has nothing wrong and that he can play, but if not I'm going to do my best for the team."

Argentina overcame injury-hit Ireland with a mix of blunt force and fluent counter-attacking, extending their fine form across the tournament.

The Pumas believe they must raise their level once more against the Wallabies, though, with Montoya wary of the influence of Australia scrum coach Mario Ledesma.

Ledesma won 84 caps for Argentina between 1996 and 2011 as a hard-scrummaging hooker, and has since carved a similarly-formidable reputation as a coach.

Relishing the challenge against Australia, Montoya admitted treating Ledesma as a role model growing up.

"It was a dream for me, I never imagined some years ago playing in a World Cup, against Ireland at the Millennium," said Montoya. "It was amazing.

"We have our scrum technique, we're working hard on that, but Ireland are one of the best packs in the world.

"I think we had a good scrum we put pressure on them, but they are still very strong, and it was a very tough challenge.

"Australia have improved so much in the scrum recently, so it's going to be a really tough battle for us there.

"It will be a great competition there, it's very exciting.

"It's always a bit strange to see Mario there for the Australia set-up, but he's done excellent work for them.

"He has helped transform their scrum.

"He's one of the great hookers in Argentina's history.

"I looked up to him, I watched him play in World Cups and a lot for Argentina.

"I think it's great to see the profile of Argentinian rugby continuing to grow."