Rory Best will lead a side that will have three players - Christian Wade, Billy Twelvetrees and Brad Barritt - making their Lions debuts in the back line having flown in from various parts of the world over the weekend - and a fourth player who will be merely 'dropping in' for a three day stint.
Shane Williams will join up with the squad to play on a third Lions tour having agreed with Warren Gatland to arrive on Monday from Japan, train with the squad, play on Tuesday and then leave on Wednesday.
"We just said we needed him for one game. He is already halfway here and part of the reasoning behind that is that he is still playing," said Gatland of his former Wales wing.
"We spoke to Shane and just said the proviso is he comes in Monday, trains, plays on Tuesday and he leaves the squad on Wednesday. He was perfectly happy with that.
"We know that he's fit and in training - he's been boxing as well, although hopefully that's not needed on Tuesday- and I'm sure he'll come in and do the jersey proud and do himself proud.
"We just went through picking a team last night, trying to look through the looking glass towards Saturday a little bit and thinking about the players. The decision was made in terms of Christian and Brad to bring them in.
"We felt that there were a number of players who were either sore or had backed up and, again, if you look at our back three we felt we were pretty short there at the moment. To give us the best chance for next week, rather than potentially playing someone on Saturday, Tuesday, then Saturday, we thought we'd be proactive and call someone in now."
Jamie Roberts is undergoing a scan on his injured leg today and George North is still struggling with his tight hamstring. Tommy Bowe's broken hand is fast improving, Brian O'Driscoll was fit enough to play on Tuesday, but wasn;t considered, and Manu Tuilagi's injured shoulder is improving.
"Today is a recovery day and we will train tomorrow. We realise it is going to be tough on a few players, but Billy and Brad know each other pretty well, and I think Shane will fit pretty well into our game-plan," added Gatland.
"Fingers crossed with Jamie. He has never pulled a hamstring before and he is not 100% sure whether that is the injury. We're hoping Manu is going to be fit, but at the moment his shoulder's still sore. He's out in training and we're hoping he's going to be fit and available for Saturday.
"Players like Sean Maitland, who is sore after last night, have had three games in a row. We are trying to give potentially our Test side the best possible chance of being fit. We want to have everyone fresh to try to win the first Test match.
"The forwards seem to be holding themselves together, and unfortunately the backs are the ones who are taking all the knocks. It is something I haven't really experienced in the past.
"When you look at probably the most attritional position out of all them, the loose forwards, they are all fit and running and ready to go. It is just one of those things that happens.
"The games have been tough and physical and Saturday night was no different to anything else we would have expected."