There are no fewer than seven Welshmen in the starting XV and a further three among the replacements. The Ospreys' provide a complete back three and six players in total to the match day 22.
O'Connell is one of eight players in the match day 22 with previous Lions experience and he will pack down in the second row with the only survivor from the triumphant 1997 tour to South Africa, Simon Shaw.
"There has been a lot of preparation over the last 12 months and a lot of work with the squad over the last two weeks. But you get to a stage where you want to be playing a game and learning and building from performances on the field," said McGeechan.
"The first game on tour gives experience to some of those players who don't have a lot of test matches under their belts. It's important to get them on early and by the end of the third game everyone will have had a start.
"The players set the ball rolling and then we build on that performance. After our first game in Phokeng the matches come thick and fast.
"It's a great feeling running on the field wearing a Lions jersey. That isn't different for any of the players, including the more experienced ones like Paul.
"We want a good performance, to get settled and to have something positive to build on."
Among the Lions debutants will be Munster's Keith Earls and Cardiff Blues' Jamie Roberts, who join forces in the centre - the same position in which both McGeechan and Lions tour manager Gerald Davies made their debuts in South Africa.
"I remember my debut against Western Transvaal at Potchefstroom in 1974 and it is a career highlight," recalled McGeechan.
"For young men such as Keith and Jamie it will be a day to remember and they will be thrilled to get an early taste of match action on the tour. Outside these guys is the proven experienced combination of the Ospreys' back three of Lee Byrne, Tommy Bowe and Shane Williams.
"While we have a lot of players making their Lions debuts there is a huge amount of international experience in the team. The average age is 28 that reflects the maturity we have in the squad.
"Scottish captain Mike Blair is at scrum half while players of the calibre of Paul O'Connell, Joe Worsley and Adam Jones have played over 50 Tests each."
British & Irish Lions Team to face Royal XV
15. Lee Byrne (Ospreys/Wales)
14. Tommy Bowe (Ospreys/Ireland)
13. Keith Earls (Munster/Ireland)
12. Jamie Roberts (Cardiff Blues/Wales)
11. Shane Williams (Ospreys/Wales)
10. Ronan O'Gara (Munster/Ireland)
9. Mike Blair (Edinburgh/Scotland)
8. Andy Powell (Cardiff Blues/Wales)
7. Martyn Williams (Cardiff Blues/Wales)
6. Joe Worsley (London Wasps/England)
5. Paul O'Connell (Munster/Ireland) captain
4. Simon Shaw (London Wasps/England)
3. Adam Jones (Ospreys/Wales)
2. Matthew Rees (Scarlets/Wales)
1. Andrew Sheridan (Sales Sharks/England)
Replacements
16. Lee Mears (Bath/England)
17. Phil Vickery (London Wasps/England)
18. Alun-Wyn Jones (Ospreys/Wales)
19. Stephen Ferris (Ulster/Ireland)
20. Mike Phillips (Ospreys/Wales)
21. Stephen Jones (Scarlets/Wales)
22. Riki Flutey (London Wasps/England)
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