"We want to improve obviously," Sabella told reporters. "There are many things we have to think about and improve.
"All players who played today have contributed to this victory but of course we have a genius who is called Messi. Fortunately he is Argentine. Everybody would have liked to have Messi but it is us who have him."
After a frustrating 90 minutes against the gutsy Iranians, Messi broke the deadlock with a delightful curling shot in stoppage time to the delight of tens of thousands of Argentine fans at the Mineirao stadium.
"It was a very difficult match and Iran played a great World Cup match. But that last play from Lionel no one could have stopped it. Not even two goalkeepers could have stopped that Lionel shot," Sabella said.
Argentina, among the title favourites in Brazil, played below par for the second consecutive game after narrowly winning their opener against Bosnia 2-1.
They may have secured qualification to the round of 16 but Sabella, who had fielded an attacking formation with Gonzalo Higuain, Messi, Sergio Aguero and Angel Di Maria, said they would analyse what had not worked that well, including breaking past the Iranians down the wings.
"This sort of thing can happen, it shouldn't but it does," said the Argentine, who won the Copa Libertadores at this stadium with Estudiantes in 2009.
"Of course we always want to win, obviously, so we will try to strike a balance in the next games but it is not always easy," he said.
Argentina, who have six points, next play Nigeria with Iran, on one, facing Bosnia in their last group game. Nigeria and Bosnia play later on Saturday.
"Sometimes during counter-attacks we decide a match but today things got a little difficult with our counter-attacks," Sabella said. "I want to congratulate Iran because they played a brilliant game."
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