"I think we were clinical with our possession," said O'Sullivan. "I think we defended very well when Samoa tried to speed the game up.
"But we were aware that we had to do that because Samoa are very dangerous as we saw in the first half. They got one break from the first mistake we made in the first half and they scored. It was a great lesson early in the game.
"We were prepared for that mentally and physically. And I think we did a good job. We had a few glitches, but over the 80 minutes we really dominated field position and possession. You could not ask for more in temperatures of 35 degrees.''
Samoa assistant coach Michael Jones was disappointed with his side's performance, but gave credit to the visitors.
"I've never seen our boys make so many mistakes in one game," said Jones. "Ireland thoroughly deserved their win. They played really smart and they capitalized on our mistakes.
"We made too many mistakes and you can't win without the ball."