The Middle Eastern outfit had frustrated their South American counterparts for much of the game in Belo Horizonte and were minutes away from claiming a deserved point.
However, a moment of magic from the Barcelona star proved enough to send Sabella's side into the last 16 of the World Cup, but the coach admits that a big improvement is necessary ahead of the knockout rounds.
"It was very difficult. We had the possession and the control in the first half and we created three clear-cut chances and had a few dead-ball situations too. Iran played a great game," he told FIFA.com.
"We have to have a good look at what happened and try to improve. We have a few causes for concern."
The Argentines face Nigeria in their final Group F encounter on Wednesday.