The Wallabies (AP)
London - Regardless of who wins Sunday's Rugby World Cup semi-final between Australia and Argentina, for one man the result is bound to be bittersweet.
Mario Ledesma, the former Argentine hooker now working for the Wallabies, faces the ultimate test of his allegiances when the two sides lock horns at Twickenham.
Capped 84 times by the Pumas, Ledesma played in four World Cups and was part of the side that made the semi-finals in 2007 so he would love nothing more than to see his beloved Pumas reach the final for the first time.
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But the 42-year-old has also pledged his commitment to Australia, joining the Wallabies as forwards coach, with the specific job of fixing the scrum.
Ledesma, a renowned master of the dark arts of scrummaging, has transformed Australia's pack from a laughing stock to a potent weapon which has given them a fighting chance of winning a third World Cup.
But to do that, they first have to beat Argentina, whose strength undoubtedly lies in a scrum that Ledesma was a big part of for 15 years.
Australia coach Michael Cheika knows the match will be an emotionally-charged occasion for his new scrum doctor and he has told him to sing both national anthems with gusto.
"It's obviously a big game for him, and he likes to shed a tear now and then in the dressing room or the team meeting just for a bit of fun," Cheika said.
"I remember when we went to Mendoza to play in the Rugby Championship and we were walking up the stairs before the match and I said to him, 'are you going to sing your anthem, the Argentine anthem?'
"And he wasn't sure if he was allowed or not. I said, 'Of course, that's your heritage', and I want him to love that."
But Cheika, who formed a close bond with Ledesma when they worked together at French club Stade Francais between 2010-12, has no doubts about Ledesma's commitment to Australia's cause.
"I know he loves this team," Cheika said.
"He loves being involved in this team and he'll do anything he possibly can this week to make sure this team is in the best-possible spot going forward."
A stickler for detail, Ledesma has gone to extreme lengths to try and unlock the problems that had plagued Australia's scrum for years, even lying down on his back in the tunnel during practice scrums to get a bird's eye view of what was happening.
He brought in new players and changed techniques, encouraging the backrowers to drive straighter through the centre of the scrum, and the results have been extraordinary.
A year ago, the Wallabies were getting pushed around by every team they played but they have not taken a backward during the World Cup.
"He keeps it pretty basic and tells it how it is. That's how I like being coached," Australian lock Kane Douglas said.
"If you do something wrong, he'll tell you.
"He gets a bit emotional, he's pretty passionate about what he wants and what we're doing. He's great to have around."