By Andrew Cawthorne
BELO HORIZONTE, Brazil, June 19 (Reuters) - Having already bettered his last World Cup with a nerve-easing first goal in Argentina's opener, Lionel Messi should lead his countrymen to an easy win against unheralded Iran in Belo Horizonte on Saturday.
Argentina started with a five-man defence in their 2-1 defeat of Bosnia but coach Alejandro Sabella should toss off the shackles and start with the players' preferred 4-3-3 against one of the tournament's most limited teams.
That tactical switch during the Bosnia game freed up Messi, and others in Argentina's "Fab Four" attackers, enabling the four-times world player of the year to score a dazzling goal that was his first at a World Cup in eight years.
"Messi could be the best player in the world - if he was human," quipped awestruck Iran coach Carlos Queiroz, saying his charges would need a "miracle" to beat Argentina.
Iran may take heart from history, though.
In their sole prior meeting, Iran did secure a 1-1 draw with Argentina over 90 minutes during a 1977 match in Madrid - albeit they then lost on penalties in a low-key mini-tournament to celebrate Real Madrid's 75th anniversary.
Asia's best-ranked side at 43rd in the FIFA standings, Iran showed their vaunted defensive abilities in a 0-0 opening draw against Nigeria against Group F.
That game brought jeers from Brazilian spectators otherwise gorged on goals in the tournament, but delighted Iran who earned their first World Cup clean sheet, and only sixth ever point, in four World Cup appearances since 1978.
If Argentina win on Saturday, they will top Group F on six points and guarantee passage to the last sixteen.
Messi, Argentina's most gifted player since Diego Maradona and desperate for a World Cup on his otherwise glittering resume with Barcelona, admitted he was nervous before the first game and urged an attacking formation from the off against Iran.
"That's how we have to carry on, like the second half (v Bosnia), we feel more comfortable that way," he said. "We have more chances to pass, the four of us go out all guns blazing."
At the other end, Iran's tricky winger Ashkan Dejagah and lone striker Reza Ghoochannejhad may not see much of the ball, but when they do, will be dreaming of prising open an Argentine defence lacking the brilliance of their strike force.
With a sole World Cup victory to their name, against political foe the United States in 1998, Iran can at least take heart from some big upsets in the tournament so far.
If Chile could conquer Spain, and Costa Rica undid Uruguay, might Iran make it a third day in the sun for the underdog? That looks unlikely given they lack the attacking spark of those giant-killers, but until Saturday afternoon all Iran can dream. (Additional reporting by Patrick Johnston and Rex Gowar, Editing by Nigel Hunt)