Argentina coach Diego Maradona admitted his side will face greater tests after their 2-0 victory over Greece at the Peter Mokaba Stadium made it three wins in succession in Group B.
Defender Martin Demichelis and substitute Martin Palermo scored the goals in the last 13 minutes after finally breaking through a determined Greek rearguard action.
"Now the road gets more difficult," said Maradona. "You always hear about Germany, Italy, Brazil playing poorly, but they're always in the second round, quarters, semi-finals and the final."
With his side virtually qualified even before they played their final match Maradona made seven changes but insisted on playing Lionel Messi and in the process he made the Barcelona forward Argentina's youngest captain two days short of his 23rd birthday.
"It was a unique experience - something very special," said Messi.
"As soon as I knew about it it was just great, unique."
Maradona also rounded on his critics, who were many when Argentina stumbled through qualifying and made it only with two wins in their last two matches.
"They (the critics) should apologise to the players, who are 100% professional," said the World Cup winner.
"We are doing our duty, which is to defend the Argentina shirt. Sometimes they are wrong, but those who have also criticised are wrong and should apologise."