Argentina head coach Alejandro Sabella has claimed that it is imperative for his side to improve defensively ahead of the World Cup knockout stages.

Sabella's side battled their way to a 3-2 victory over Nigeria in their final Group F fixture on Wednesday, but he admits to feeling slightly concerned about Argentina's defensive frailties.

"We are an offensive team and, as such, there will be some questions about the defence," the 59-year-old told members of the media. "The defence is doing a great job, but we must study ways on how to improve it.

"If you make mistakes like that in the round of 16 you'll be punished. I am satisfied with the qualification and what we've done so far, but we must look to improve."

Argentina will meet Switzerland in the last 16 next Tuesday.