Argentina rightly drew plaudits for an excellent attacking display in their Rugby World Cup quarter-final victory over Ireland, but Juan Imhoff believes that their defensive effort was the key to victory at the Millennium Stadium.

Six Nations champions Ireland were fancied by many to reach the semi-finals for the first time in their history, but the Pumas ran in four tries in an excellent 43-20 triumph.

Wing Imhoff scored twice for Argentina, who saw Ireland cut the deficit to just three points having trailed 17-0 inside 15 minutes.

And Imhoff says that Argentina's resolve to fend off an Irish comeback was crucial to their success.

"We are a very good team in offence, we attack very well," he said. "But our defence made the difference.

"It was a very tough game. We worked hard to get this victory, now we want to enjoy the moment but we know we've got another hard game to come."

Joaquin Tuculet arguably scored Argentina's most important try when he crossed the line in the 68th minute to ensure Ireland would need two scores.

The full-back feels Argentina's progress to the semi-finals is just reward for their hard work, but warned they will have to up their game to come through the semi-finals.

"We have to improve to reach the final. We have worked hard in the last four years and this is a good team," he said.

"We have good staff and if we work hard we can make the final."