The master Dutch tactician has to factor in four players on yellows -- defender Craig Moore, defensive midfielder Vince Grella, attacking midfielder Tim Cahill and striker John Aloisi -- as he devises a strategy to upset champions Brazil in Munich.

Croatia's spirited performance in going down 1-0 to Brazil on Tuesday has underlined the challenge that faces Australia in Stuttgart next Thursday in their bid to make the second round in their first finals in 32 years.

The meticulous Hiddink, whose daring all-out attack policy sparked Australia to a memorable late 3-1 win over Japan last Sunday, is irritated by the 'stupid' yellow cards conceded in the opening victory.

"I have my concern with the yellow cards, it's a big concern for the next game because two tough games, two world-class teams, not just Brazil, but Croatia on me, so it makes a huge problem for me," Hiddink told reporters after Thursday training.

Should any of the four players receive another yellow card or caution against Brazil they will be automatically suspended from the Croatia showdown.

"Some of our players weren't controlled enough and got some stupid yellow cards which makes the condition on the next game and the final game," Hiddink said. "I am thinking about it (resting players), we've talked about it and there were two or three stupid cards in my opinion, but it makes a condition on the next game."

Socceroos eyeing 'cup final' against Croatia

Newcastle United defender Moore, sensing the precarious situation he is in should he play against Brazil and risk a further card, said he was prepared to step down from Sunday's starting eleven if Hiddink deemed it.

"Of course, I want to play, but then if it means maybe missing a massive game against Croatia, that's going to be our cup final to progress (to the second round), then I'll just see what the situation is," Moore said.

Australia realize what confronts them against the Brazilians and their so-called 'Magic Quartet' of goal scorers, Ronaldinho, Ronaldo, Adriano and Kaka, but also know that they could conceivably put themselves in an even better situation to take in against Croatia with a result against the odds over Brazil.

"We have a feeling that why don't we pull ourselves over the line now and take the foot off the pedal ever so slightly for the last game (Croatia)," defender Lucas Neill said. "The result might determine whether we're first or second and that would be a fantastic position to be in."

"There's no pressure on us because Brazil are the world champions and everybody expects them to win, but why not, we believe we can get something."

Dutch-based midfielder Jason Culina said of the Brazilian challenge: "They're number one, but we've already played the number three in the world, Netherlands, and we did well against them (1-1 draw in Rotterdam), so anything's possible. There's no awe in playing against Brazil, a lot of our players have played against some of the biggest players in the world in the past so we're not going to be star struck, we're going out to do our best."

But pragmatist Hiddink knows his team are up against a monumental task to come away with something from the five-time world champions. "I've watched Brazil for a long time, if it's not going well they take a 1-0 (against Croatia) and they grow into their shape, but we try to make a good game and give them a hard time."

"We try to make some surprise, but it's almost too much."

Health fears surround non-firing striker Ronaldo

Meanwhile, the Brazilian were playing down fears that off-par striker Ronaldo is suffering from a rather more serious ailment than a lack of form. The Real Madrid striker was taken to hospital in Frankfurt after feeling unwell but medical tests showed nothing wrong with him, the Brazil Football Confederation (CBF) said.

The CBF said on its website that the 29-year-old started feeling unwell on Wednesday evening after the Brazilians had returned to their Königstein base following the 1-0 win over Croatia in Berlin.

The Brazilian medical team whisked him off to a Frankfurt hospital, but he returned to join the squad after medical tests cleared him and he was expected to train normally on Thursday.

Ronaldo was the star of the last World Cup in Japan and South Korea, scoring both Brazilian goals in the 2-0 win over Germany in the final.

But his form has slumped over the last year as he has struggled with weight problems and he is expected to leave Madrid during the close season. He was widely criticized for his lackluster performance against the Croatians on Tuesday.

Coach Carlos Alberto Parreira, however, has said he intended to play him in the Brazilians' next game against Australia on Sunday.

The Brazilian famously played in the 1998 World Cup final in Paris against France despite being taken mysteriously taken ill shortly before the kick-off. France went on to dethrone the Brazilians with a 3-0 victory.

Ronaldo needs just one goal to move ahead of Pele as Brazil's top all-time World Cup goal scorer. Both currently have 12 two behind all-time goal leader Gerd Müller of Germany.