Only 16 months ago, the Saracens centre was out on loan at Bedford but on Saturday night he will take his place in a new-look England team vying to retain the Calcutta Cup.
Farrell proved he has the big-match temperament when last season he guided Saracens to their first Aviva Premiership title with a victory over Leicester in the sold-out Twickenham final.
The 20-year-old believes that experience is the perfect preparation for Saturday's opening Six Nations clash in Edinburgh.
"The team gets picked on form and nothing else. I am looking forward to getting stuck in," Farrell said.
"The build-up is different but (the mindset) doesn't change for me whether the crowd is 82,000 or 6,000. Once you get out there you have a job to do and that is what you have got to focus on.
"I am looking to take the atmosphere in, I am looking to enjoy it and hopefully thrive off it. It's what you play rugby for, to enjoy those moments.
"I try to take my nerves and put them into excitement. As I walk out I have a huge smile on my face. I take the occasion in - and then it's game-time."
Farrell is one of three debutants in England's starting side, with Saracens centre partner Brad Barritt and Northampton number eight Phil Dowson also preparing for their Test bows.
The last time England fielded two debutant centres was in 2002, when Geoff Appleford and Ben Johnston played in a 26-18 win against Argentina in Buenos Aires.
Farrell, Barritt and fly-half Charlie Hodgson, who will start his first Test in four years this weekend, have built up a successful relationship for Saracens.
"We know each other inside out now," Farrell said.
"We have been playing together all this year but it is not just that, we are good mates. And when you are going out there to play big games you put your body on the line for your mates."
Dowson gets his chance at number eight after six years playing for the second-string England Saxons. At times he wondered whether his debut cap would ever come.
"The first thing I did was phone my sister Louisa. She asked me why it took so long," said Dowson.
"I played my first Saxons game in 2005, a lifetime ago in sports terms. I've tried to use the experience of not being picked as motivation to get here and it's finally paid off.
England's interim head coach Stuart Lancaster has named another five uncapped players on the bench for the Calcutta Cup showdown as he looks to build "a team for now and a team for the future".
Lancaster's starting line-up boasts just 236 Test caps, including Lions appearances, compared to Scotland's 501. The Scottish pack alone has more international experience than England.
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