It was an early "danger sign" for rest of the AFL, recalls Greg Swann. Having trialled for a month at Carlton during 2009, homesickness had got the better of Ciaran Sheehan. He opted to head back to county Cork. Sheehan had appeared the more talented of the pair of prospective Blues spotted by recruiting staff in the Emerald Isle.

But talent isn't everything. Not when you're moving to a faraway land to pursue a career in a sport with a different shaped ball, a game in which only a small fraction of Irish aspirants succeed.

Yet Zach Tuohy was unperturbed by Sheehan's choice to go home. He remained resolute in his desire to make it Down Under. On Sunday, that fierce determination to overcome obstacles will reach a statistical materialisation, when the boy from county Laois becomes just the fifth product of the "Irish experiment" to play 100 VFL/AFL games. Tuohy will join Jim Stynes, Tadhg Kennelly, Pearce Hanley and Sean Wight in reaching triple figures, exclusive territory given the more than 50 Irishmen who have chanced their arm the competition over the past three decades.

Then Carlton chief executive, Swann – who is now at the helm of the Brisbane Lions - hosted Sheehan and Tuohy during their stay in Melbourne. "That was a big thing when Ciaran Sheehan went home because they were together at my place. So [Tuohy] was left on his own, but it didn't really worry him," Swann said.

"He was just like 'no, no, I'm here for a reason and I'm seeing it through.' So that was probably for me the danger sign if you like. He toughed it out."

Sheehan eventually came back, deciding to give Australia a proper go ahead of the 2014 season. Once on equal footing to Tuohy, Sheehan now looks at his countryman as perhaps the prime exemplar of what Irish players can achieve in the AFL. Looking back to 2009, Sheehan said Tuohy always had the characteristics needed to make it. "One thing that stood out to me was his determination and his drive to succeed. He was always a very driven person," Sheehan said.

Sheehan, 25, along with fellow Irishman Ciaran Byrne, 21, is an international rookie at Carlton. Neither has to look far for a role model.

"The main thing [Tuohy] said to us was 'just to focus in on what people are saying, and try and take in as much information as possible.' That way you get the best out of yourself and I suppose you learn a bit faster," Sheehan said.

"It's a bit daunting coming out here. People are pulling you left, right and centre – telling you 'how you do this' and 'how you do that'."

Byrne, who, like Sheehan, has been plagued by injuries in his two and a bit seasons at Ikon Park, says Tuohy's support has been priceless.

"Zach understood what it was like for us as young kids coming out here, trying to learn the new game.

"Even the simple things, like doing a bit more kicking with him was always handy. Having him here has been great."

Restricted to just a single AFL game and two VFL matches due to ongoing hamstring troubles, the highly-rated Byrne did it tough, sidelined halfway around the world. "It was a very difficult year for me. Just having Zach around as that witty type of bloke. On your bad days he's get you up and about, and simple things like going for coffee … it was good to have him around," Byrne said.

Byrne had already borne witness to the Tuohy approach when trialling at the club in 2012. "My very first two weeks in Australia, coming out here as a 16-year-old kid. I got to spend two weeks living with Zach, and I saw how professional he was and the way he went about things."

Sheehan had played four games at the end of 2014, but he too was a onlooker during Carlton annus horribilis, a groin issue proving his undoing. But Tuohy was there for his old mate.

"He's helped me out a couple of times. Obviously I haven't had the smoothest career to this point. I've been a bit up and down with injury. But Zach's always been the type of fellow that has just told me to 'keep going, keep persisting with it, and your opportunity will come'.

"He's met me for coffee and just told me how important it is to keep your head down and work hard and that opportunity will come. He always looks to the positive side of things. He always brings out the best of people that way."

Daring defender Tuohy finished third in the Blues best and fairest last year. Of course it is tempered by the fact Carlton claimed the wooden spoon and had a coach sacked. But it was nevertheless a remarkable effort for a man playing just his sixth year of football, and who made his senior debut midway through 2011.

Not that Tuohy's progress has surprised Swann. He saw the signs right from the start.

"You could tell early on that he was a good player. He kicked it better than most of our guys and you could tell he had something about him," Swann said.

Veteran sports agent Gerard Sholly played a central role in bringing all three of the Blues' Irishman to Melbourne. While he had the physical attributes and skill to make it, Sholly thought Tuohy's success has had more to with mindset than anything. "I think it's testament to his determination. Irish guys are usually athletic, and they play a high level of sport in their own country, so we know that they're good enough in terms of the athletic side of it," Sholly said.

"But to stick it out takes a lot of determination and is incredibly difficult for them off the field. [But] he's a tough individual, off the field and on the field. He's able to absorb that pressure and that homesickness."

Irish players tend to feel most homesick when experiencing "FOMO" – the fear of missing out – on family and sporting milestones back home. Yet Tuohy has endured. Two years ago he spoke to Irish AFL hopefuls during a camp in Dublin. He didn't sugarcoat the challenges either. Sholly said that Tuohy knew how hard things could get.

"There are probably times when he's felt, 'can he last the distance, should he go home?' But he's overcome all those mental stressors."

Any such issues appear to have faded away now, not least given his partner Rebecca is Australian, and son Flynn was born here. Whether he stays here post-career remains to be seen, but if Kennelly and and Stynes are good guides, there will be a role in the sport for the bearded Blue when he hangs up the boots.

Tuohy is just 26 though. There should be much still to come.

The Carlton list has undergone wholesale change, meaning Tuohy has catapulted into the "experienced" bracket at the club He is not just a leader of the Irish trio, he is a leader of the club. Byrne thinks there could be higher honours to come for the former rookie. "Especially in the last two or three years he's shone in that area, and his leadership qualities have really been very good. There's no reason why he couldn't be captain in a couple of years."

In any event, Sheehan suggests that the best is yet to come for the man who is set to join only Robert Walls in playing 100 games in Carlton's No.42 guernsey.

"He's in the best shape he's ever been in. He's been improving as the years went on. He's on track to being one of the best defenders in the comp."