The Triple Crown holders are currently plotting a course to win their first RBS Six Nations crown in 20 years, following opening wins over Italy and Scotland.
O'Sullivan, who expects a "very physical'' encounter with England on February 27, said: "The improvement in Irish rugby is based on the strategic plan by the IRFU to centrally contract the players and manage them.
"It has been a massive advantage because it has allowed us to develop the strength of our players. This has been key to our development."
Meanwhile, Newcastle Falcons boss Rob Andrew has ruled his injured fly-half Jonny Wilkinson out of contention for England's trip to Lansdowne Road later this month.
The 2003 World Cup drop goal hero damaged a ligament in his knee when playing against Perpignan in the Heineken Cup last month, but reports that he could recover in time have been denied by Andrew.
"Jonny will not be fit in time for England's game against Ireland but he has a chance of being ready for the matches with Italy and Scotland," said Andrew. "Charlie and Olly Barkley are proven kickers in the Premiership - but there is a lot more pressure at Test level. We have seen Jonny prove he can handle it in his career, but he's not ready yet to return. We are monitoring him closely."
Wasps winger Josh Lewsey - a try scorer at the weekend, and now one of the elder statesmen in Andy Robinson's England side, commented on their impending Dublin trip: "Ireland are obviously the favourites for the tournament - and rightly so.
We've got to go there with two defeats and try to rectify that," said the 28-year-old. "We know we have got the players to do it, but we are up against it. We've got a week away now, and I think that will be healthy to have a bit of a break from each other -and then we come back fresh.
"There is no point in going over to Dublin and battening down the hatches. I don't think that suits our game - I don't think the players want to play like that and I don't think the coaches want to play like that," he added.
"Hopefully it will be a dry day, although I don't think I have ever been to Lansdowne Road, and there hasn't been a gale blowing from one end to the other!"