It left him as a virtual shoo-in to be named in Warren Gatland's touring party and after being selected, Halfpenny is now preparing for tomorrow's first Test against the Wallabies.
Halfpenny endured Lions agony on the 2009 tour to South Africa, the then 20-year-old forced to fly home after failing to recover from a thigh injury.
But with those problems behind him, Halfpenny can now focus fully on taking on Australia and he says the role of Jenkins has been vital to his progress.
"Jenks can only do so much. It is up to us to go out and perform," said the Cardiff Blues man.
"But he has been massive in terms of my preparation for every game. He was the best in the world in his day and I couldn't think of anyone better to have bringing on the tee for me and giving me little pointers just before the kick and things.
"He has just been massive for me in terms of my progression through the years and preparing me mentally and technically."
Jenkins has worked with kicker Halfpenny within the Wales squad and is fulfilling the same role on the tour Down Under.
The hard work seems to be paying off. Halfpenny's first game of the tour saw him land nine conversions and two penalties in a faultless kicking performance against the Western Force.
His first try of the trip came against the Combined Country before two scores, four conversions and four penalties saw him end with a 30-point haul against the New South Wales Waratahs.
While Australia have remained tight-lipped on the identity of their kicker, Halfpenny's form so far will mean he is almost certain to kick against the Wallabies.
"We all know how fine the margins are between winning and losing in international rugby and how often kicks decide the outcome," he said.
"I am obviously pleased with the way things have gone in the last couple of games.
"But that's gone and it's about getting back on the pitch now, putting in the hard work and making sure I'm as prepared as best as possible to go into Saturday. Hopefully I'll continue with how it has been going."
As well as being dependable with the boot, Halfpenny's attacking game has flourished while in defence, his speed to cover opposition kicks is one of the most underrated aspects of his game.
And while he regularly nails kicks at goal, Halfpenny argues he enjoys all parts of his No. 15 position.
"I really love every aspect of the role of full-back," said Halfpenny.
"I love the aerial battle, I see it as a challenge between myself and the guy chasing. Owning the sky, I like to call it. I love it.
"Every time that ball goes in the air, the challenge has been put up there - who is going to collect it? It is an area we have worked very hard on throughout."