Chile may be without influential duo Alexis Sanchez and Arturo Vidal when it begins World Cup 2018 qualifying against Brazil, according to Jorge Sampaoli.

Both the Arsenal forward (knee) and Bayern Munich midfielder (groin) have been included in the Argentine coach's squad but have arrived carrying knocks picked up on club duty.

And while Sampaoli remains unsure if either of them will be able to feature in the newly crowned Copa America champion's opening clash with Brazil, he still feels Chile has the quality to begin its campaign in a successful manner.

"They are both in the same condition. I cannot confirm at this stage if either will be fit to face Brazil," the 55-year-old said in a news conference. "Of course, they are very valuable to us but I am confident that if they are not available we have the squad to be competitive against Brazil or Peru."

Dunga's side suffered a quarterfinal elimination from the 2015 Copa America at the hands of Paraguay, but Sampaoli still believes Brazil poses a significant threat.

"Starting the qualifiers against Brazil is the worst possible scenario," Sampaoli said. "They are still the greatest power in the world, despite all the criticism, and they have elite players."