"Throughout the day there was a few nerves but as soon as I got called, I just forgot about everything. I just got into it and was just like I was playing rugby anywhere else," he said afterwards.
"It was a seriously tight game - they don't get any tighter than that. I felt comfortable when I came on and I didn't feel out of my depth, so I suppose that's a positive from my point of view."
Notably, the Leinster back rower was one of four 22-year-olds on the Irish bench on Saturday, alongside his provincial colleague Martin Moore and Ulster duo Iain Henderson and Paddy Jackson.
A look back at the Ireland Under-20 squad from the 2010/11 season reveals that six players have now gone on to win senior caps - Murphy, Moore, Henderson, Jackson and fellow 22-year-olds Craig Gilroy and Luke Marshall.
With the even younger Stuart Olding and Robbie Henshaw (both 20) also making the step up to Test level last year, it shows that the age-grade coaches and structures are bringing through players who are well able to break through onto the international stage.
Indeed, Murphy is the 15th Irish player to have played Junior World Championship rugby (since 2008) and gone on to win a Test cap, following in the footsteps of Rhys Ruddock, Conor Murray, Peter O'Mahony, Simon Zebo, Gilroy, Jackson, Henderson, Marshall, Stephen Archer, Ian Madigan, Olding, Dave Kearney, Jack McGrath and Moore.
Murphy had two seasons with the Ireland Under-20s and played for the Emerging Ireland team in the Tbilisi Cup last summer before making his debut with the O2 Ireland Wolfhounds against England Saxons last month.
The Lansdowne clubman has really kicked on with Leinster this term, scoring four tries in 13 appearances including Heineken Cup scores against Castres Olympique and the Ospreys.
Murphy said he experienced 'mixed emotions' when coming off the pitch on Saturday evening, disappointed by the narrow 13-10 defeat to England but obviously pleased to have earned his first Ireland cap.
Looking at the Championship picture after Ireland's first defeat, he admitted: "We know we're still in with a chance (of winning the Six Nations), we're just disappointed we didn't get the win.
"What's the point in biting each other's heads off? We've still got a Championship to win and we're still in with a possibility (of winning it).
"Everyone's a professional player, we know that defeat is part of it and we've just got to move on."
Part of that moving on process will be a two-day training camp in Belfast this week, as thoughts turn to the visit of Italy to the Aviva Stadium - a team Murphy knows will be 'firing and looking for their first win'.
Being part of the starting line-up or matchday squad for that particular game will be the former Blackrock College and Ireland Under-19 captain's next goal.
"(The back row) have been outstanding throughout the campaign so far. From my point of view coming on, I just have to look to fit in straight away so there's not an imbalance there.
"I'm watching them (Jamie Heaslip, Peter O'Mahony and Chris Henry) throughout the game, looking at the things they're doing right and looking to emulate it when I come on.
"I would relish playing in any international game, playing for your country. I obviously got a few minutes and now I've got to train well. Joe (Schmidt) will make the decision in the coming weeks."
Murphy's versatility - he has played for Leinster at blindside, openside and number 8 - will certainly stand to him as he looks to move up the international pecking order.
It will be interesting to see how the young forward progresses as he could be the subject of a quiz question to stump all Irish rugby fanatics.
Six Nations statistician Stuart Farmer has informed us that Murphy is the first Ireland international to be born in mainland Europe since the Allen brothers (Glyn and Ellie), who were born in Gibraltar and played for Ireland in the 1890s and early 1900s.
Murphy was born in Barcelona to his Dublin parents Conor and Nicola and spent the first nine years of his life in Spain, before a permanent move back in Ireland in August 1999 where he was enrolled in Willow Park School and soon started playing rugby.