They might be opponents on Sunday but there has been no lack of friendly banter between Leicester Tigers team-mates Geordan Murphy and Martin Castrogiovanni.

The pair will line up on different sides at Otago Stadium when Ireland tackle Italy in the crucial Rugby World Cup Pool C clash.

But there is an enduring friendship between the two, who play for last season's Aviva Premiership finalists and co-own a restaurant in the city.

"I'm thinking of leaving him some baskets of chips in the corners of the pitch; that should distract him (Italian prop Castrogiovanni)," Ireland fullback Murphy said.

"I tend to drink a lot of water and he tends to eat a lot of food and that's probably got something to do with his hair loss!"

"But he's a good mate of mine, a fantastic prop and he's very passionate about his rugby. He's a different character off the field than he is on it."

"He's certainly one of their key players and one we know we have to target this weekend.

"He's been texting me regularly. He swears a lot at me in Italian and tries to teach me all the bad words to say."

Castrogiovanni, with his flowing locks and powerful, aggressive scrummaging, has become one of the cult figures of the World Cup and scored a try (his 11th in 80 Tests) in the 27-10 win over the United States in Nelson on Tuesday night.

Murphy is one of the characters of the game in Ireland. At 33, he has been awarded 72 Test caps since his Test debut in 2000 and he toured New Zealand with the British and Irish Lions in 2005.

He has watched the gradual improvement of Italian rugby during his career.

"They want to get to the quarter-finals for the first time in a World Cup. They're a serious side and they've improved massively," Murphy said.

"It's a massive game, the biggest in our pool. They'll raise their intensity from the Six Nations. This is the World Cup."

Ireland and Italy are effectively  in a knockout situation with Australia expected to comfortably beat Russia in Nelson on Saturday to confirm their place in the quarter-finals.

Ireland are likely to face Wales in a quarter-final if they can beat Italy and then another Six Nations team, either France or England, if they can make it to the semi-finals.

But Murphy said the Irish had not even thought about the likelihood that their knockout opponents would all be from the northern hemisphere.

"We're just focusing on Italy," he said. "We know we'll be in bother if we look ahead any further."