FIFA World Cup Qualifying: Chile v Venezuela
Farias' side will travel to Santiago for Friday's game, which could have a major bearing on who qualifies for Brazil 2014.
Venezuela are currently sixth in the standings - level on points with fifth-placed Uruguay - while Chile are well-placed to earn automatic qualification in fourth.
However, Farias' team could see their chances of reaching next year's showpiece damaged by illness.
"They didn't have a good night and they weren't able to train well," said the manager.
The bug represents an undoubted setback for Farias, who was previously in bullish mood ahead of the clash in the Chilean capital.
"The key is to stay focused on each match and not be thinking about the other results," he had stated.
"The only option for us is to earn our own points.
"We will work to the end for it. We know it will be difficult but it is time for us to play to our best and deliver for all who have trusted and dream of hearing the national anthem in Brazil."
Meanwhile, Chile know that eight points from their final four matches will see them qualify for next year's tournament, and their squad was supplemented by the arrival of six players on Tuesday.
Claudio Bravo, Francisco Silva, Carlos Carmona, David Pizarro, Matias Fernandez and Bryan Rabello all joined up and will be available for selection for manager Jorge Sampaoli.
Dinamo Zagreb striker Junior Fernandes will also be in contention for a place in Sampaol's side, as he has been called up to replace the injured Humbarto Suazo.