Keith Wood confirmed his retirement this morning after Ireland's crushing 43-21 defeat to France in their World Cup quarter-final.
"It's time to hang up the boots," said the hooker, who has played 58 Tests in a career spanning nine years and three World Cups. "My desire is still there - I would play for another 10 years if I had the chance.
"The head is willing and the heart is willing but the body has had enough," he said, admitting his shoulder injury had been the key issue.
"The injury to the shoulder is an injury that is waiting to happen and I'm lucky to get out before I make an absolute mess out of it. I knew I was going to retire whenever the end of Ireland's involvement was.
"It's been a privilege to play for so long."
It was ultimately a sad way for Wood to bow out as Ireland were blown out of the water in the first half by France, and O'Sullivan admitted it was almost impossible to staunch the French flow.
"We were battening down the hatches every two minutes only to have them ripped off again," he said of a first half which saw France 27-0 up by half-time.
"They really got a stranglehold on the game early on," he said. "Fifteen minutes in it was 14-6 on line-outs and 9-3 on penalties. If that was a boxing match we would have been in real trouble because we were getting hit from every side."
But he praised his players for bouncing back and scoring three tries in the second half.
"It took a lot of character to go out and go at the French and not give up," he said. "In the last 30 minutes we played a lot of good rugby and we didn't give up anything in the process."
He paid tribute to the all-round game of the French, and suggested they could win the World Cup for the first time.
"I've been involved with playing with France for many years and they've always had flair and always had power," he said. "But I think at the moment there is a clarity of thought in this French side that is very menacing.
"Their discipline is superb and on top of that they've got exceptional speed. If they get that sort of form in the next round I think they can go the whole way. France can beat England, and I think England know it."