Key midfielder Arturo Vidal looks set to miss Chile's World Cup opener against Australia in just four days.

The Juventus star again did not train with his teammates at their base in Belo Horizonte, Brazil on Monday with inflammation in his knee and is racing the clock to be fit for their clash with the Socceroos in Cuiaba on Friday (Saturday AEST).

Arturo Vidal, right: set to miss the clash with the Socceroos. Credit:AP

Some Chilean media outlets are reporting he's not only likely to be ruled out of the Socceroos encounter but may also miss Chile's second group B match against world champions Spain on June 18.

Some reports suggest coach Jorge Sampaoli may be considering cutting him from the squad altogether with Rodrigo Millar to be called in as an injury replacement.