Over the past twelve months, Munster man O'Callaghan has been Ireland's most-used lock. He started seven of Ireland's 11 internationals last season and came on as a replacement in the other four. O'Connell, owing to a hand injury, missed the 2005 Autumn internationals but made his comeback against Italy last February in the RBS 6 Nations - he played in a total of seven Tests.
Meanwhile, Ireland's record caps holder Malcolm O'Kelly also made seven starts last season, the last of which came in the Triple Crown-clinching win over England at Twickenham.
Shane Horgan, Brian O'Driscoll, Ronan O'Gara, Denis Leamy and Andrew Trimble run through a sprinting drill. Ireland can do all the preparation in the world to combat the Springboks' teak-tough defence, but captain O'Driscoll has admitted his men will have to play what's in front of them at times tomorrow, and not work off set plays.
The Leinster centre said: "South Africa's defence is probably the most aggressive in the game. People think they play a specific format but they are very smart in that they have guys shooting out of the line. You can never tell which one it will be so there is a method to their madness as well.
"It's very hard to plan a certain set of moves to break down this defence because it changes with every play. You just have to try and make sure you don't get frustrated by defences like that. Wasps adopted a similar style over the last few years.
"You have to play what's in front of you rather than have set plays. Maybe this is when natural footballing ability comes to the fore."
Ulster's Paddy Wallace, who will be the back-up number 10 tomorrow evening, was a pivotal member of the Ireland side that won the Under-19 FIRA World Youth Championship in France back in 1998.
Wallace, O'Driscoll and O'Callaghan, three members of the Ireland 22 for tomorrow, were all starters during that tournament which saw the Irish beat South Africa on an appeal. After finishing 17-17 at full-time, the South Africans claimed a 4-3 penalty shoot-out victory but lost out when an appeal confirmed that one of their goal kickers had not actually taken part in the match.
Kildare man Geordan Murphy started both the June Tests against New Zealand, but he lost his starting place at full-back to Girvan Dempsey for the subsequent defeat to Australia and also for tomorrow's game. Admittedly, the Leicester Tigers star cuts a nervy figure on the bench.
He said: "It is a difficult situation to be in but I think Girvan is a really nice guy and we get on well, on and off the field. It is just one of those things you have to do and you can't let it affect you. One of us was alway going to be disappointed and this week it is my time.
"I don't like being on the bench and I will be itching to get on - although thankfully I haven't had too much experience of being on the bench. I find it quite difficult because you're very nervous, but it's one of those things that just has to be gone."
Gordon D'Arcy gets by Simon Easterby in training - the Leinster centre will come face to face with another big man tomorrow in the form of South African midfielder Jean de Villiers. D'Arcy will be giving away almost a stone in weight and four inches in height to the 6ft 2in-15 stone 'Bok, but he is more than comfortable facing bigger opponents.
He said: "He (de Villiers) is a lot bigger than I am, which isn't hard! He was a big force during the Tri-Nations. He's a strong, dynamic runner who is very direct. South Africa use him to make ground up the middle.
"But I had some good preparation for him by playing against Edinburgh's Rob Dewey for Leinster recently. He's a big guy as well so they are similar opponents. I'll do my homework on de Villiers and look for a few chinks in the armour - I'll work with the back row in containing him."
Ireland number 8 Denis Leamy will be completing a cherished set when he lines out against South Africa tomorrow - it will be his first cap against the Springboks and third appearance against one of the Southern Hemisphere's big hitters in the space of five months.
The Tipperary man, who has played in 14 Tests in three different positions, is determined to hold onto his starting spot. He said: "Initially I played at number eight as an experiment to see how it went. Things went well and I've played there for a number of games.
"You always have to keep on top of your game and make sure you're playing well, because there are so many quality players in the back row - especially at number eight.
"You don't dwell too much on losing the jersey but you have to be realistic - look at the guys behind me like Jamie Heaslip. They'e playing really well and they keep you on your toes."
Ireland out-half Ronan O'Gara has averaged just over 10 points in his four appearances to date against South Africa. He kicked a conversion and two penalties in the 28-18 loss to the 'Boks in 2000, collected 17 points (1 conversion, 3 penalties and 2 drop goals) on the 2004 summer tour and famously bagged all of Ireland's points in their 17-12 defeat of South Africa two years ago - that was a try, three penalties and a drop goal.
Gordon D'Arcy reckons Ireland's form on the 2006 summer tour, despite the three defeats, has shown that they can compete with the world's top teams. He added: "You don't need too much motivation to be playing one of the top three sides in the world. After the summer tour (to New Zealand and Australia) we know we're there or thereabouts.
"A phrase that Drico (Brian O'Driscoll) has used over the years is 'we don't want to be a nearly team.' We want to move onto the next level and to do that we need to be beating teams like South Africa and Australia on a regular basis."
**All photos by Lorraine O'Sullivan of Inpho Photography**
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