The 29th-ranked side fell to a 3-1 defeat in Greece in the first leg of their play-off on Friday, conceding two goals from Konstantinos Mitroglou and a Dimitris Salpingidis strike.
The visitors could only muster a solitary Bogdan Stancu effort, leaving them with a mountain to climb in the return leg in Bucharest on Tuesday, and Piturca knows Romania need to be better defensively.
''I expected a difficult night and that's what it was,'' he said. ''They took the lead so quickly after the equaliser.
"And I don't want to talk about the third goal. It looked like something that happens in a school playground.''
Romania are aiming to qualify for the World Cup finals for the first time since 1998, when they reached the second round.
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