article_snippet: Sergio Aguero posted an Instagram picture of Martino .
article_snippet: Ezequiel Lavezzi (back row, centre) posted a picture of Argentina team-mates after joining the squad in US .
article_snippet: Sergio Aguero also took to Twitter on Monday to upload a picture with the backdrop of the Washington Monument . '
article_snippet: Martino told a news conference at Argentine FA headquarters. '
article_snippet: Messi helped guide Argentina to the 2014 World Cup final before losing to Germany .