Luke Fitzgerald went straight from school into Leinster's senior set-up. Most promising kids have the good grace to stop off along the way at the club game and pay their respects before moving up to provincial level. But the Leinster coach Michael Cheika asked him if he would like to hang out for a while with the Academy set. "It was a no-brainer for me really," Luke says. He went with the big boys.

Now, three years later, the 21-year-old wing and the other big boys are preparing for tomorrow's Heineken Cup semi-final against Munster at Croke Park. It is expected to attract the biggest crowd ever to watch a club rugby match, and is another stepping stone on Fitzgerald's remarkable trail from Ireland's grand slam victory to flying out to South Africa with the Lions later this month.

It is in his blood. He was not long out of nappies when his dad, Des, was playing for Ireland against Australia in the 1991 World Cup quarter-final, a match Ireland lost by one point to a try in the final seconds. Some years later – a lot of years – and aware that his old man had once been a cornerstone of the Ireland team, he sat down to see what all the fuss had been about.

"When he was playing I wouldn't have had a breeze what was going on," he says. "But since then I've seen him in that World Cup game with Australia. And I saw him floor some fella in a game – against Scotland I think. I haven't seen much footage really and even what I have seen you can't see much of him. It was a different game back then: scrum after scrum after scrum.

"But in that Australia game their backs got their hands on the ball a fair bit. The likes of Campo [David Campese], [Bob] Egerton and Timmy Horan and these fellas – quality players. The Irish guys were probably up-and-under merchants."

In this case father and son are polar opposites in their rugby lives. Des Fitzgerald was a suitably belligerent tight- head prop who won 34 caps between 1984 and 1992.

Towards the end of his career the winds of change were beginning to blow through rugby's committee rooms and while the idea of rugby as your living was already a target in the southern hemisphere, in this part of the world it was seditious stuff.

As for his son, rugby is all he knows. "I was 18 [when I joined Leinster] and I wouldn't have changed it for the world. Fantastic. It was daunting enough at the start because you're with all these guys you'd seen playing for the national team like Brian O'Driscoll and Shane Horgan but you get over the 'awe factor' pretty quickly because you're competing for a position with them week in week out. Once I got over the star-struck bit I really enjoyed it and the team spirit was fantastic."

Just as well because he says there was no Plan B on his list of career options. He had started out doing an arts degree in University College Dublin, more as cover than anything else, but once the deal was signed with Leinster he reversed out of college at speed.

"I'm doing business studies in the Open University over in the UK at the moment. It never really crossed my mind what I'd do if rugby hadn't worked out. I was always trying to get some back-up in case it ever did fail but since I was about five or six years old I always wanted to be 'there' if you know what I mean. I didn't want to be doing anything else."

He is not too bad at it either. This season alone, for example, he has already picked up ¤55,000 (£49, 100) for his Grand Slam exploits with Ireland and stands to lift that to almost ¤100,000 from a summer with the Lions in South Africa.

And that is before you factor in any bonuses for getting to this point with Leinster. Of course, in that regard the only bonus he is interested in is getting to the final in Edinburgh on 23 May.

The only previous time these teams met in Europe was at Lansdowne Road in 2006, at the same stage of the competition, when the entire country stopped to watch Munster's 30–6 victory. He was there as a supporter in his Leinster schools jersey, along with a mate of his.

"Yeah, it was so disappointing and it's one of the things that we're... we're not trying to rectify it because it's done now and you can't rectify it, but it's another game with Munster that we're trying to win. And I don't think that defeat will have any bearing whatsoever on this game.

"My experiences against Munster have been good until the Magners game in the RDS [Arena] this season. That was the first time I'd lost to them. I'd played against quality Munster teams from school through to professional and while they were always titanic battles I had a clean sheet until this season, which was pretty disappointing.

"There's no baggage, though. They're things in the past and that stuff only motivates you for totally the wrong reasons. There's enough motivation as it is: it's a Heineken Cup semi-final; it's in Croke Park; it's against Munster. What more would you want for a big day out? Just think positive thoughts."

Fitzgerald does not come across like the type of player with any space in his head for negativity.

"Ah no, like the next person there's the odd negative thought that pops in there but when it comes to rugby it just doesn't help. It's another thing that stops you playing to your potential. I've never gone into a rugby game thinking I couldn't win it."

He would have fitted in nicely with the Aussies from another era.