But he recovered to make his first start as Joe Schmidt's troops bounced back to see off Scarlets 15-10, handed the No.7 jersey for the first time.
However at just 20-years-old, Murphy knows he has got plenty more work and isn't about to rest on his laurels ahead of the visit of Aironi.
"You've got to get the jersey and give it back the way you found it," he said, about his first start in Wales.
"Just because you get picked at a young age, it doesn't mean you can think you are running the show.
"There are guys who have worn that jersey with great pride and done a good job in it.
"You've got to try to do the same, if not better, every time. You can't put in a bad performance when you play for Leinster. I think that is what he (Schmidt) meant when he talked about responsibility."
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