All eyes will again be on Lionel Messi as Argentina look to smooth their passage into the World Cup last 16 by claiming top spot in Group F.

The South American giants are already assured of a place in the knockout stages in Brazil after two Messi-inspired victories.

The Barcelona star struck a stunning late winner against stubborn Iran on Saturday to complement his great solo effort in a 2-1 defeat of Bosnia-Herzegovina.

Yet while Argentina might be in command of the group, they are not yet assured of first place and could be denied by Nigeria if they lose to the Africans in Porto Alegre on Wednesday.

Nigeria have four points from their two games and while a point would suffice for progress, the probability of avoiding France in the next round provides an incentive for victory.

As ever, Messi will be the man to stop. He may be yet to fully fire - in common with team-mates Sergio Aguero and Angel di Maria - but he has shown with his two goals what a world-beater he is.

Argentina coach Alejandro Sabella said: "All the players contributed to the victory (against Iran) but of course we have a genius who is called Messi.

"Fortunately he is Argentinian - everyone would like to have Messi but it is us who have him."

There remains some debate over Argentina's most effective formation.

Sabella's 5-3-2 against Bosnia did not really suit, but they were also troubled as they played with 4-3-3 and 4-3-1-2 variations against Iran.

That may give Nigeria hope of causing them further problems but the Super Eagles have also not hit their stride, playing out a goalless draw with Iran and labouring to a 1-0 win over Bosnia.

Fans have been critical, particularly of the lack of potency up front, and the complaints have riled coach Stephen Keshi, who this week hit back.

"England and Spain are out of the World Cup, and nobody in those countries has raised hell about their teams' performances, but yet we get criticised for drawing against Iran," Keshi told reporters.

"The fans have gone to the extent of insulting the players and their families. So how will they get inspired or motivated?

"They keep insulting the players, and yet you want them to keep playing for Nigeria? If I were a player now, I'd stop playing for the national team.

"It is a shame what our fans are doing. They thought Iran was easy but they saw how difficult it was for Argentina to beat them.

"To be honest, I'm hugely disappointed. They should just give us a break.

"You have to support your team to the end, not insult them."

Nigeria trio Victor Moses, Godfrey Oboabona and Reuben Gabriel are all injury doubts for the match.