The Juventus midfielder is struggling with a knee injury and could miss the entire group stage but the South Americans should still comfortably see off the Group B minnows.
There are fears he could even now miss out on the group stage entirely having undergone an operation in a bid to resolve the problem, after another Serie A-winning campaign with Juventus.
Despite the likely loss of the team's heartbeat in midfield, Chile is expecting progress from a group containing both 2010 finalists, Spain and the Netherlands. That is a measure of the ambition and expectations of the team's quixotic Argentine coach Jorge Sampaoli, who replaced the under performing Claudio Borghi in December 2012.
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Sampaoli is a coach who is determined to stick by his attacking principles and his teams - particularly his highly-successful Universidad de Chile side of 2011 - have had the typical, pulsating hallmarks of his philosophy. Sampaoli has placed his trust in a number of key performers of that team like Eugenio Mena, Charles Aranguiz, Eduardo Vargas and on-field lieutenant Marcelo Diaz.
Complementing that band are some players who have made their names at the very top level in Europe. Aside from Vidal and Sanchez, goalkeeper and captain Claudio Bravo has earned plaudits in Spain with Real Sociedad and is likely to join Barcelona this summer.
If Chile has a settled side and a clear identity, then Australia comes into the tournament as somewhat of an unknown quantity. German Holger Osieck made heavy work of qualifying the team for Brazil 2014 and a pair of 6-0 defeats in friendlies to Brazil and France cost him his job. He had long since lost popular support as a result of his dour football and reluctance to breed a new generation of Aussie internationals.
Replacement Ange Postecoglou is a renowned A-League coach and has wasted no time in replenishing the Australian stocks. Out have gone established names like Mark Schwarzer, Lucas Neill and David Carney and in have come 13 players with 10 caps or fewer to the tournament.
Expectations for the team barely stretch beyond a hope to avoid embarrassment and Chile is a tough first assignment for the side ranked bottom of all 32 qualifying teams.