Three matches played, three matches won. And three different centre partnerships used. A fourth variation - captain Brian O'Driscoll in tandem with 67-cap heavy hitter Kevin Maggs - starts against France on Saturday, but O'Sullivan has no qualms about the changes.
Especially when you consider the Irish midfield will outweigh the visitors' pairing of Yannick Jauzion and Ludovic Valbon by 124 Test caps to just 25.
"The weather is more likely to impact on the game plan than the changes made. We have worked as a squad for a long time and Kevin comes in knowing exactly what his role will be. Brian knows exactly how Kevin plays and it shouldn't be a problem,'' insisted O'Sullivan.
"It does change the dynamics about how we play, but we do that from week to week depending on the opposition. Gavin (Duffy) is on the bench - a very versatile player who has been at full back, wing and the centre as well. We have options available to us because we have versatile players either on the pitch or the bench."
''In this particular season it might be perceived as a new challenge for both of us but it's not really because we've been there and done that together in the past."
Someone who will appreciate Maggs' midfield graft and guile is former France centre Jo Maso - team manager for the current les Bleus.
The 60-year-old - who lost twice to Ireland as a player in 1969 (17-9) and 1973 (6-4) - conceded: "It was already difficult to win at Lansdowne Road when the Irish were not playing so well. We know now, we will have to have our helmets on!"