As former Wallabies coach Bob Dwyer suggested to Fairfax Media on Tuesday, Cheika's Argentinian set-piece coach, Mario Ledesma, has been up-skilling one the five props in the squad – and as flagged, that prop is Scott Sio.

The former Pumas hooker sees no problem in having only two specialist hookers in the squad – those being captain Stephen Moore and Tatafu Polota-Nau – and recalled how he was one of only two hookers in Argentina's squad at the 1999, 2003, 2007 and 2011 World Cups.

"We played … with two hookers and a prop who can play hooker," Ledesma said. Asked who the back-up hooker is, Ledesma grinned and then said: "That's a surprise."

Pressed on the issue later, Ledesma said: "If we have an injury that lasts only one week, we'll make the prop play. If it lasts longer, we just have to get the other hooker [James Hanson from the train-on squad] who has been training with us every day."

Under Rugby World Cup law, if either Moore or Polota-Nau are injured they must be withdrawn from the squad altogether for another specialist hooker to be brought in – that being Hanson.

If not, a player already in the squad with hooking skills must cover for that position.

Ledesma conceded he had been training up one of the Wallabies props as cover.

Then when asked if that is Sio, 23, the scum guru smiled and said: "That's a possibility."

Asked if the choice of Sio is him having had some experience at hooking in school rugby level, Ledesma said: "Yeah … it wasn't too difficult [to work out], hey?" and then laughed. However, Ledesma was adamant that there would be no need "to convince" Rugby World Cup authorities that Sio, at 115kg and 187cm, would be equipped as a hooker.

"When you go in to a game you have to say who is playing tight or loose [head prop] – or if they are playing both," Ledesma said of official formalities in team selection. "If we don't put it there, they cannot play on either side; but if you put it there, nobody is asking you, 'Is this guy able to play both sides?' [With] the hooker, [it] is the same. I mean, he is a prop. It is not like we are playing a No. 9 as a hooker. That would be dangerous; but a prop as a hooker … there is no danger there."

Ledesma said he has not been overloading Sio with extra tuition in the hooking role. "No … we are trying to prioritise," Ledesma said. "He is working as a prop, and a little time here and there we will be working [on hooking]. But I'm real comfortable with 'Taf' and 'Squeak' [Moore] and if they get a serious injury, the third hooker will come. That is how a lot of teams have been doing it. I played four World Cups. We did every World Cup like that and nothing happened."

Meanwhile, Ledesma believes the Wallabies scrum is no longer seen as a weak link.

"I think it was much more of a perception," Ledesma said. "But I just think we have to put the scrum in the place that it deserves here in Australia … [that] of being a really, really important part of rugby … if not we will be playing rugby league."

Ledesma cannot mask his love of scrummaging. "I am very passionate about a lot of things … the scrum being one of them, but rugby is a big passion of my life," he said. "I am coaching scrums so I put all my passion in the scrum. There is nothing more humbling than the scrum. You can dominate a scrum, and then the next one get smashed."