Murphy will be on the wing against Italy - and the 30-year-old remains determined to put in a big performance in front of a sell-out crowd.
"The injury has always been in my memory bank - and when I was selected for the Scotland game (two weeks ago), I was asked was I worried about breaking my leg again," said the Leicester player.
"So I didn't have the luxury of completely putting it out of my mind."
Players cannot afford to think like that, Murphy believes. "Once the whistle goes, all fears sort of go out of your mind," he said.
"It's a relief to be named in a World Cup squad. We're not there yet, so anything can go wrong - but it's not something I think about.
"I'd rather play well and get injured than not play well."
Equally adept at full back or on the wing, Murphy is also considered Ireland's third fly-half behind Ronan O'Gara and Paddy Wallace.
But with a World Cup looming large and injury problems in the Ireland back division, he knows he could cement a starting place if he impresses against Italy.
"Some people may think it is a curse being versatile, because you get pushed around in the team - but I'm quite happy to play anywhere," he said.
"It's a great honour to play for your country; it's a little bit tough when you're getting moved up and down the back line.
"It would be nicer to be in one position - but I'm just happy to be in the shirt.
As well as posing a threat to Italy with his skill and pace on the wing, Murphy can also provide his coach Eddie O'Sullivan with the inside track on the opposition.
Murphy added: "I know a couple of their guys, because I play my club rugby with Martin Castrogiovanni and I've been introduced to quite a lot of his Italian friends.
"Italy are a very strong side; they have improved immeasurably over the last few years and they are real contenders now.
"They are a very big side, and when they put their game together they are pretty impressive.
"Castrogiovanni is a big boy. But he is quick as well - he was Leicester's player's player of the season last year. He is a huge asset and a very good prop."