The likeable 30-year-old plotted the downfall of an understrength Ireland team last May and June and Sunday will see him trying for a repeat against Ireland's elite at the Parc des Princes, but will it affect those friendships back in Dublin if the Pumas prosper?
"Before this week, I was friends with the boys and I have been in contact with them, mostly with Darce (Gordon D'Arcy) and the other Leinster players although not this week because I have to wear my country colours," Contepomi admitted.
"But one thing rugby gives you is friendship and in a few weeks I will be back at Leinster, training with these players. My friendship with these men goes beyond rugby and I would not lose that, not even for one game."
Whereas his own team have risen to the occasion in France, Ireland have strangely looked below par in their pool games so far. Admitting that the Irish need a "miracle" result to make the quarter-finals, Contepomi also feels that they have it within them to turn their fortunes around, especially with the number of world class players they have dotted around the field.
"With any crisis in life, you can overtake it or sink. They will have to perform a "miracle" to score those four tries and not let us score a bonus point, then they will be through and we will be out of the competition. So, when you are in that sort of situation, you can turn it positive if you have the mental strength.
"You have to see why they are in this situation - if there is a problem between the players or a problem on the outside. I doubt there is a problem between them (the players). The guys I know at Leinster are very easy-going, very united and so I can't imagine that there is a problem there," he added.
"I think when you go into a competition every four years you need that bit of luck and perhaps the Irish have been lacking that.
"You go through name-by-name and they have players who are among the best, if not the best, in their positions around the world. D'Arcy and (Brian) O'Driscoll are, for me, the best centre partnership in the world and their combination can be lethal. Shaggy (Shane Horgan) and Denis Hickie are two of the best wingers and then you have Geordan (Murphy) who has world class quality from full-back.
"But games are won and lost in the forwards and they also have a pack that know each other, six or seven play for the same club (Munster) all year-round, so you look at Ireland and see that they can very easily turn this around. We need to be focused."
Contepomi and his countrymen have been happy with their performances and results to date at the 2007 tournament - a shock five-point defeat of hosts France and a brace of bonus point wins over Georgia and Namibia - but there is always room for improvement and that could come this weekend.
"There are areas we definitely have to improve. Our lineouts, scrums and restarts could be better. We also have to remember that in the last two games we started on the back foot, so it's very important that we make the same start against Ireland as we did against France in the first game," Contepomi said.
"We are happy the way the tournament is going but we are very conscious nothing has been achieved. I don't care about what they (Ireland) have to do. We know exactly what is required and hopefully we can dominate the game and get the right result.
"We are a very unified squad and are enjoying the World Cup experience because we are in a position we did not think we would be in. But it could all end if we do not control our own performance. We know, with this Irish team, we could be out by Sunday," he added, with a touch of caution.