With four players invalided out of the tour last weekend - Gethin Jenkins, Adam Jones, Brian O'Driscoll and Jamie Roberts - McGeechan has had to dig deep within his squad to field a competitive side.
"It is fair to say injuries have had an impact on the tour as you would expect including selection for the third Test as we were unfortunate to lose Brian O'Driscoll, Jamie Roberts, Gethin Jenkins and Adam Jones through injury last Saturday," admitted McGeechan.
"However, the players coming into the starting XV are all talented international players and are as keen as ever to turn the tables on the Springboks. Last Saturday we were minutes away from winning and that is a huge positive to take into the Third Test.
"Andrew Sheridan, Joe Worsley and Martyn Williams will all be part of a Lions starting XV for the first time. Stephen Jones, Mike Phillips, skipper Paul O'Connell and Jamie Heaslip will earn the distinction of being in the starting XV for all three Test matches.
"As a squad, they have met many challenges on the tour including playing two matches per week, the inevitable injuries and two narrow Test losses. Despite this they have remained a tight, focussed squad and I know those playing in the Third Test will give their all to ensure that we achieve a victory on Saturday.
"A Lions tour is a unique experience for players in the busy, modern professional rugby calendar. The 2009 Lions have thrown themselves into the spirit of the tour, have interacted with the people of South Africa and shown themselves to be great ambassadors for northern hemisphere rugby."
Tour manager Gerald Davies believes the Lions are determined to end their 10-match adventure on a high at Coca Cola Park and says the whole trip has been a great experience.
"The tour has been a wonderful experience and the team spirit has confirmed the best traditions of the Lions continues. The tour concludes on Saturday with the third and final Test in Johannesburg," said Davies.
"The players are determined to ensure that all their hard work during the 10-match tour is rewarded with a Test victory. There is no doubt that little has separated the British & Irish Lions and the Springboks so far in what has been a tremendous series - Saturday should prove to be another great match."