The 25-year old Bayer Leverkusen winger ruptured his anterior cruciate ligament at training on Friday and is now set to miss the rest of the Bundesliga season as well as the 2014 World Cup which takes place in June and July this year.
Postecoglou admitted that Kruse's presence from his Socceroos squad will be missed in Brazil but is banking on the former Brisbane Roar and Melbourne Victory ace bouncing back from the disappointment.
"I heard last night and my primary concern is for Robbie as a player because he's been denied the opportunity to represent his country at the highest level at the biggest sporting event in the world later this year," Postecoglou said yesterday.
"It is a tough break for Robbie, who was playing some great football and was certainly a massive part of our plans for the World Cup.
"It's fine to say he'll get another chance but you just never know and I feel for him as the 2014 World Cup was looming as a great opportunity for Robbie to show the world what he is capable of.
"It will have an impact but for me the primary concern is for the player in this situation."
Postecoglou added: "One positive is the fact he is young and I know he'll work hard on his recovery and come back a better player.
"There is a carrot of an Asian Cup on home soil in 12 months and he will play a big part in what we are trying to achieve with the National Team."
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