Understandably, the provinces reacted angrily to the move and voiced their frustration at being denied access to their best players for the opening fixtures of the season.

But after seeing his side out-muscled by the Springboks over two Tests during the June tour, O'Sullivan remained adamant the regime was imperative if Ireland were to be successful in the international arena.

And he was proved correct on Saturday as a bulkier Ireland emerged for the Dublin showdown against South Africa and proceeded to register only their second victory over the reigning Tri-Nations champions.

“In South Africa we felt that we struggled physically against the Springboks because they’re a huge side,” said O’Sullivan.

“We matched them on Saturday and a lot of the credit for that goes to the work the lads did during the summer.

“There has been a bit of flak about the 10-week training and fitness program but we knew we had to get the players bigger and stronger to compete.

“We are bigger and stronger than in June and that was a big factor in the win. We were able to stay the pace, meet South Africa head on in the tackle, to hit hard and carry the ball at them.

“It was also hard work for them to stop us. That didn’t happen by accident - it was because of the hard graft from the players during the summer.

“There’s more work to be done in that area but the result was proof that that period of time was very valuable.

“To beat the Springboks you have to stand up to them physically – you have to fight fire with fire.

“If you’re being bullied off the park you can’t play rugby. Rugby is a physical game and a lot of the time that’s where it starts and finishes.”

O’Sullivan insists Saturday’s triumph was only part of an on-going process aimed at creating Ireland sides who are capable of beating southern hemisphere opposition on a regular basis.

“We’ll take the win and put it in the bank. You can’t rest on your laurels,” he said.

“We are setting standards for ourselves but you don’t sit back on them. We need consistency and we do dip below the barrel some times, like we did in June.

“We left that Test behind us on the tour and that used to keep me awake at night for a while, wondering if we would ever beat the Springboks. The more often you cross the line the more you believe you can do it every time.

“We’d be foolish to think we’ve turned the corner. It’s an ongoing job because the southern hemisphere sides are getting better as well. But we’re getting there slowly but surely.”