Not only that, four of the threequarter line have only been in Australia for a matter of days and the team had only one training session ahead of a game against the top Super Rugby franchise in the country.
But Irvine, a veteran of three tours as a player, is happy with the decision to draft in players from around the world to ensure no more pressure is put on back line numbers ahead of the first Test against the Qantas Wallabies in Brisbane in four days time.
The former Scotland full back, who is still the Lions' record points scorer with 274 in 42 games, knows all about the problems of coping with injuries on tour having seen no fewer than eight players head home from his final tour to South Africa in 1980. Even so, the Lions won all 14 provincial matches and one of the four Tests.
"The coaches made a great call in trying to preserve the players for Saturday, so that we have a fresh team with a bit of luck. The boys who play in Canberra have a massive responsibility because we want to go through the tour undefeated," said Irvine.
"Tuesday's game will be a really tough encounter because the Brumbies are a hell of a side and they will be targeting us. Where we are right now is unusual because normally it is the forwards who take the battering.
"It is an incredibly physical game now, even more so than in 2009, but strangely it is our backs who are struggling. And that's despite the fact they've won the physical battle in every game on tour and have been wonderful in their bravery, defence and taking the game to the opposition."
Irvine has no qualms about the new players fitting into the side for a massive one-off effort against the Australian Conference champions and he can't wait to see how Shane Williams gets on after his emergency SOS.
The 36-year-old former Ospreys and Wales wing, now playing in Japan, will become the oldest back to play for the Lions when he takes the field in Canberra for what will be his 15th appearance for the Lions on a three tours.
"Shane has been an absolute genius - he is true box office. I just love watching him play. He is in good condition and he will fit into this team because he is a class act," added Irvine.
"We have to be realistic - it is an unusual team for Tuesday, but these boys will be up for it. I've worked with any number of teams over the years, but I can't think of a better set of lads than we've got here
"There is a lot of character in this team and there is a great combination of youth and experience. The older players are really showing what experience counts for by helping the younger ones, who are bubbling with enthusiasm.
"There is a great mix and team spirit and Sam Warburton is doing a great job as captain. The likes of Brian O'Driscoll, Paul O'Connell, Jamie Heaslip, Adam Jones and Alun Wyn Jones are all contributing and they are all working together.
"So far things are going well, but we've got a bit of an injury situation to deal with at the moment. Hopefully, it might be short term - we just don't know. But if we can come through Tuesday night without any more problems we will have a better idea of where we are."