Alejandro Sabella has admitted that he has a "few causes for concern" as his Argentina team needed an injury-time winner from Lionel Messi to beat Iran this evening.

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.