Two wins from their opening two Group F games mean Lionel Messi and company face Nigeria here on Wednesday with their passage to the last 16 assured.

Argentina must improve and find greater mobility to cope with the imminent threat posed by Nigeria and to make further inroads at this World Cup, coach Alejandro Sabella suggested in Porto Alegre on Tuesday.

Two wins from their opening two Group F games mean Lionel Messi and company face Nigeria here on Wednesday with their passage to the last 16 assured.

But only Messi's stoppage time strike saved the day against Iran, the Barcelona star also got the winner against Bosnia-Hercegovina, and Sabella is only too aware Nigeria are an altogether different proposition to the Iranians.

"We have to improve, starting with myself," he told an eve of match press conference at the Beira-Rio stadium.

"We need more mobility to find spaces, Nigeria are a different team altogether than Iran, with high potential and they play very quickly and switch into attack very quickly.

"Against Iran we got lost on the pitch in the second half. What happens is when you are so eager to win a match to get qualification you lose your balance."

Asked how he felt about the criticism the performances in Brazil so far have generated back home he replied: "I'm not worried about that, my only worry is that we have to improve. And we are improving, little by little."

Tens of thousands of fans are expected to drive across the Argentine border to this southern port city to either attend the game or be on hand to support their side.

"We know that Argentinian fans are passionate about football, they've proven that again by the numbers who came to Rio and Belo Horizonte. I can imagine how many will be here tomorrow."

Among those set to be at the stadium to cheer Argentina on are members of the country's two World Cup winning teams in 1978 and the 1986 side including Maradona.

"It's a matter of pride they are coming, but I don't think we'll have much time to say hello and thank them," observed Sabella.

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