Twelve years ago Paul O'Connell made his Six Nations debut for Ireland in a match that he barely remembers. During the game, for much of the first half, his memory was even hazier – for he was oblivious to both his surroundings and try-scoring exploits.

Of course, being O'Connell, he had made an instant impact against Wales as a raw 22-year-old. "I scored a try but I don't remember it. I went to tackle Craig Quinnell and he knocked me clean unconscious with his elbow. I played on for another 25 minutes, scored a try and then, eventually, with seven minutes left in the first half, I came around. I didn't really know what was going on and so I walked off the pitch. The doctor came over and he was asking my phone number and holding up his hand and saying how many fingers. While he was questioning me I looked up at the clock as it was counting down. It said 2 minutes 19. I told the doctor: 'Mick, I'm not coming off after 2 minutes 19 seconds. Mick said: 'There's 2 minutes 19 seconds left of the half. You've played the whole half. You scored a try.' I argued with him: 'I didn't score a try. You're only saying that to get me to come off.' That's when he said: 'Look, you're not going back on.' I saw the video later and I did score but I have no recollection of it."

All these years later O'Connell, who will captain Ireland again when the Six Nations begins this weekend, leans back in his chair and smiles. At least he can recall the build-up to that surreal game against Wales in 2002. O'Connell lingers over a sheet of paper listing Ireland's team and, as a lock forward, it is inevitable he should focus on the pack that day. "Munster … Munster … Munster …" he says softly, ticking off the provincial identity of his fellow forwards.

"Look at that," O'Connell says once he has completed his scan of the eight forwards and scrum-half on his debut. "All the way down from 1 to 9 there's only guy, Simon Easterby, not from Munster."

O'Connell has always played for Munster and, last week, he signed a new contract which will keep him in Limerick until 2016. His form in recent weeks, during towering Heineken Cup performances, has been exceptional yet again. The only source of wonder is that this amiable giant off the field continues to bring such ferocious commitment to his play a dozen years since that woozy first international appearance.

"This time 12 years ago," O'Connell says cheerfully, "I felt full of excitement. It also seemed like pure luck I was even in the squad. Malcolm O'Kelly was injured and I'd just been picked to start for Munster against Stade Français in a Heineken Cup quarter-final. I got man of the match but that was my first big start for Munster. I never thought for an instant I'd be involved in the Ireland side.

"I went into camp and I was rooming with Peter Clohessy [the gnarled old Munster prop-forward known as The Claw]. I said to myself: 'Why have they got me rooming with Peter? Are they trying to tell me something?' Rob Henderson then said: 'Wouldn't it be amazing if you played on Saturday?' I went [O'Connell cocks his head]: 'Is he actually thinking that or is he taking the piss?'"

O'Connell was duly picked and he looks surprised even now – recalling the first of his 88 caps. "It feels like another life. And it is another world away in comparison to the way we train, how I train and prepare, and in comparison to the person I am today. I'm more mellow. I still am very competitive but I can control it. I couldn't control it back then. When things weren't going our way I'd lose it. But there have been so many experiences in terms of winning and losing. And of course, personally, we've had a little boy and last year me and Emily got married. I can safely say I'm a completely different person from that guy who was knocked out on his debut."

O'Connell, even more than Brian O'Driscoll, remains at the imposing heart of an Irish team whose potential was made obvious last November when an epic Test against New Zealand saw them surrender the lead, heartbreakingly, in the 80th minute. This will be O'Driscoll's last Six Nations but O'Connell has committed himself, at 34, to two more seasons of international rugby after this campaign.

"It wasn't always clearcut," he admits. "If I had reached the stage I thought the IRFU weren't going to do a satisfactory deal, then I would've been happy to look abroad. Part of that would almost have excited me because I've been playing rugby here all my life. But I always felt we were going to do a deal that we'd both be happy with – and it's great I'm staying. It's important because, owing to my injury profile, I need to be with people who know my body. If you go to a new club you have to make an impression and you don't want to be stepping out of things and saying: 'Oh, I can't do this or that.' It would look odd. But I do all my own stuff – everyone will be over there and I'll be over here doing the work that best suits my body. So it makes sense to stay."

Aside from his clear happiness in Limerick a part of him understandably regrets not sampling a different rugby culture. "France would have been fascinating. Absolutely. It's going to be a real regret that I didn't do it when I was younger and experience it then. I've only ever lived in Limerick and, while I love it, it's a real shame not to have played rugby anywhere else. But I've made the right decision and I've learned what suits me in the gym and what gives me most bang for the buck – and not just doing things for the sake of it. So that's why I'm in a good place. And I've been playing OK in recent weeks."

It should be pointed out that "OK" for O'Connell is translated differently by others. "Paul O'Connell is phenomenal," Gloucester's head coach, Nigel Davies, said after the lock had led Munster to a crushing away win in the Heineken Cup this month. "He galvanises his team. His sheer presence is a huge factor." Rob Penney, Munster's coach, echoed that assessment. "Paul is an amazing character … a once-in-a-lifetime player. You wouldn't want anyone else guiding your ship."

O'Connell is more circumspect. "After the Lions tour I got married and then, in my first week back, I hurt my hamstring. I missed a lot of pre-season running and so I started slowly. But since Christmas I've been feeling really good. I'm back to where I want to be for this tournament."

A Six Nations tournament after a Lions tour is always an evocative experience for players who came together from four distinct countries. "Even more than my previous tours I got to know guys from different nationalities really well in Australia. I got on great with Ian Evans [the Welsh lock]. He's very funny and I probably spent the most time with him in Australia. But I got on incredibly well with so many guys and the coaching staff. It's not easy because you have to bare your soul. And that's difficult when you don't really know the people in the dressing room. I'm very confident speaking to a room full of Munster men. I can say what I like and in the way I want – but with the Lions it's more difficult because they don't know you at first. So I had such respect for Gats [the head coach, Warren Gatland], Andy Farrell, Graham Rowntree and Rob Howley. They made it a successful series and a very happy tour with no egos. It means the world to every player because, since that 1997 tour of South Africa, the Lions have become everything. You want to be a successful Lion who gets on the DVD – just like in 1997."

Has O'Connell watched the latest Lions DVD? "No, no! I haven't watched the '09 one either. It's cringey looking at yourself talking like that."

O'Connell captained the Lions in South Africa in 2009 and last year he was chief support to a more reserved leader in Sam Warburton. "I felt very comfortable with Sam," he says. "I would probably bark and chirp a lot. I did the same with Brian when he was Ireland's captain. Brian says more than Sam but he'll be quite quiet as well. I would bark and chomp away and Brian would chip in with some well-chosen words."

Did O'Connell, who was injured, have to do lots of talking behind closed doors when O'Driscoll was dropped by Gatland for the final Test? "Look, Brian is very experienced. He was gutted but he handled it really well. In a way the manner in which he handled it contributed to such a big performance. I was really disappointed for Brian because when you play with him so long you become biased – particularly as a forward. It's not just because of his tries but because of the way he defends and hits the ruck. You'd love to have him in the forwards. So you become a fan and I felt really sorry for him. But I felt sorry for Gats as well and the reaction he got. It was a tough way to end the tour."

Since then, under their new coach, Joe Schmidt, Ireland were lacklustre during a limp autumn defeat by Australia and then magnificent the following week against New Zealand. "Against Australia we were getting used to playing under Joe. He's an excellent, highly detailed coach. I remember Gatland said to me in 2009 that the more you think in rugby the less physical you're going to be. You either play a game plan where you don't have to think a lot so you can be intensely physical – or you make sure you know the detail inside out so it's part of your subconscious.

"Against New Zealand the details were much more familiar. So many of the things you see Leinster [whom Schmidt used to coach] doing at provincial level are harder in internationals – but we managed to do it. So, with Joe, it's definitely getting easier. Even in this camp, on the first few days, you couldn't get a spot at the laptops because the guys understand that Joe wants you to know your detail. The earlier you know your detail the better you will perform."

Apart from the final 30 seconds of that All Black defeat, when New Zealand completed an extraordinary 24-22 comeback after being 19-0 down, Ireland took fresh belief that they can match the world's best team. "Absolutely," O'Connell says, sounding as clear as he was muddled on his long-ago debut. "The standards are there. We just have to hit them week in, week out and we haven't always done that with Ireland. The one time we did was in 2009 when we were injury-free and that played a massive part in our winning the grand slam. But I think the team we've got going into this tournament is just as good. I feel really confident about our chances."