Socceroos boss Ange Postecoglou says he simply couldn't take the risk of carrying players under injury clouds to Brazil after ending the World Cup dreams of three players on Tuesday.
Defender Curtis Good and midfielders Adam Sarota and Josh Brillante were left out of the Socceroos' travelling party of 27 which will fly out on to the tournament Wednesday.
While a wealth of midfield options was the reason youngster Brillante missed out, concerns over the fitness of Good (hip) and Sarota (knee/groin) meant Postecoglou made the agonising decision to leave them at home.
"It wasn't easy," Postecoglou told reporters at the team's hotel on Tuesday.
"Obviously players being so close to getting on the plane to a World Cup and being part of it, it's not the best news to deliver.
"They have taken it professionally and understand that I'm sure their opportunities will come again. A couple of decisions were made just because of their bodies not being able to hold up.
"With Curtis, we wanted to give him every chance. We had a timeline in our heads and we tested him out a few days ago and he just couldn't get up to where we needed him too.
"With Adam, he's just come back from a knee reconstruction first year. We didn't think he could carry through with the training and the tempo."
Postecoglou dismissed concerns over the fitness of right-back Ivan Franjic, who limped from the field with a knee injury in Monday night's lacklustre 1-1 draw with South Africa.
The Socceroos boss said he wasn't worried about the team's defensive depth, despite giving the highly-rated Good every chance to prove his fitness and a shaky performance from Alex Wilkinson and Ryan McGowan against Bafana Bafana.
Centre-back Matthew Spiranovic (ankle) and vice-captain Mark Bresciano (back) missed the friendly but more out of precaution than any major worry for the tournament.
Postecoglou must still trim his squad further, with four more players to be cut from the final 23 on June 2.
Asked if he had a final squad in mind, Postecoglou said: "It's nice to work in definitive measures but the reality of football is that every day things change.
"We had a starting line up in our head all week but had to change it four or five times...that's still going to be the case right up until we play Croatia.
"You just don't know how the players are going to cope with all that. To say I have 23 in my mind I don't.
"It's up to the remaining 27 players to realise how quickly the opportunity they now have in front of them can evaporate."
Despite the scrappy performance against South Africa, Postecoglou is adamant the side remains on the right track for their World Cup opener against Chile on June 14 (AEST)
"Whilst you want to win every game and it would give everyone a warm and fuzzy feeling if we won, from our perspective it's about being ready for game one in the World Cup," the Socceroos mentor said.
"As part of that process we're doing certain things that maybe affected last night's performance but I've seen how hard our guys are training.
"The intent was there but sometimes some over exuberance and a bit of fatigue made things scrappy and we made some poor decisions but it’s all part of the process."