Published Thursday, 25 June 2009
Full-back Rob Kearney, wing Luke Fitzgerald, hooker Matthew Rees, prop Adam Jones and lock Simon Shaw all gain call-ups for a game the Lions must win to retain any chance of taking the three-Test series.
Kearney replaces Lee Byrne, who has been struggling with a foot injury, while Kearney's fellow Ireland Grand Slam winner Fitzgerald takes over from Ugo Monye.
Monye blew two gilt-edged try chances during a 26-21 first Test defeat in Durban last Saturday.
McGeechan has responded to South Africa's scrummaging demolition job five days ago by changing two thirds of the front-row.
Ospreys tighthead Jones now has the task of coping with Springboks scrum destroyer Tendai "The Beast" Mtawarira, taking over from England World Cup winner Phil Vickery, with Rees packing down instead of Lee Mears alongside Jones and Gethin Jenkins.
It is the first time the Lions have started an official Test match with an all-Wales front-row since 1955.
The selection of Kearney and Fitzgerald makes it an all-Ireland back three with Tommy Bowe, while Shaw finally makes the Test side after 16 matches and three tours in a Lions shirt.
Shaw, 35, first toured with the Lions in South Africa 12 years ago, although Saturday will be his Test debut.
McGeechan said: "As a squad, the Lions still have everything to play for.
"The players know that the outcome of the Test series comes down to Saturday, and they are determined to take the series to a decider in Johannesburg.
"There were many positives to come out of the first Test that we have built upon this week.
"We know we will have to step up our performance to ensure that we again take the game to the opposition and are more accurate in taking our opportunities."
McGeechan's second Test line-up comprises seven Irishmen, six Welshmen and just two from England - Shaw and flanker Tom Croft.