Lionel Messi and Neymar are experiencing very different qualifying campaigns with their countries

With just six rounds of fixtures to go in the South American section for qualification for the 2018 World Cup, every game is now crucial.

The top four teams will qualify for Russia, and the fifth-placed team will advance to the inter-confederation play-offs. Brazil - unbeaten in their last 11 qualifying games - are four points clear at the top, but there is an intriguing chase going on behind them with just five points covering the next five teams.

Among those struggling to keep pace with Brazil are 2014 World Cup runners-up Argentina, who face a nervy four games in order to cement their place in Russia. Here's the state of play and what to look out for...

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