Argentina's captain Agustin Creevy faces a race against time to be fit for this Sunday's World Cup semi-final against Australia.
And if he fails to make the side his place could be taken by hooker Julian Montoya who said of his skipper: "We're very hopeful that Agus will be able to start.
"He's the captain, he's an excellent player, an excellent person, so he's very influential."
The 21-year-old Montoya has 14 Test caps and has come off the bench four times during the World Cup, including for the last 25 minutes of their quarter-final win over Ireland.
The Pumas will face a Wallabies team whose scrummaging has improved greatly in recent months under the tutelage of former Argentina international Mario Ledesma.
Montoya added: "We still haven't studied it in-depth but we know them and that their scrum will be extremely tough because they've come a long way.
"Australia wasn't really a scrummaging team and now they're very good at it. It will be very close, and for us it's great if they scrummage a lot because it'll tire them.
"I don't know Ledesma but I know he's been very instrumental in improving their scrum."