The once unfathomable prospect of a World Cup without Lionel Messi and Argentina could become reality on Tuesday as South America's thrilling 2018 qualification battle reaches its climax.

Two years after Argentina kicked off their troubled campaign with a 2-0 defeat at home to Ecuador, Jorge Sampaoli's side travel to Quito to face La Tri once more with their hopes hanging precariously.

The two-time World Cup-winners head into the final round of games in sixth place overall, outside the top four positions which grant automatic qualification and trailing fifth-placed Peru, who occupy the playoff spot, on goal difference.

Yet with only two points separating third-placed Chile (26 points) with seventh-placed Paraguay (24), any number of permutations are possible.

Argentina can simplify the equation for their fans, however, if they manage to take all three points.

A victory would guarantee they finish no worse than fifth place, putting them into a two-legged play-off against New Zealand they would be expected to win.

But achieving victoty in the thin air of Quito, which is 2,850 metres (9,350 feet) above sea level, may be easier said than done.

The Argentinians have an abysmal record in away games against Ecuador, with their last victory in Quito coming in 2001.

Since then in World Cup qualifying games, they have been beaten twice, in 2005 and 2009, before scraping a 1-1 draw in 2013.

Moreover, Argentina face their moment of truth after a series of uninspiring performances that has left the rest of the footballing world scratching its head at how a squad bristling with so much attacking talent has found scoring so difficult.

Despite being able to call upon Messi, Sergio Aguero, Gonzalo Higuain, Paulo Dybala, Mauro Icardi and Angel Di Maria throughout the campaign, Argentina have only scored 16 times in 17 games.