Chile manager Jorge Sampaoli has implored Alexis Sanchez to rediscover his very best form this Saturday.

The Arsenal forward has been quiet in recent Copa America matches after a very bright start at the CONMEBOL tournament which has prompted Sampaoli to urge the best out of his star man.

Chile meet favourites Argentina at the National Stadium in Santiago on Saturday and the La Roja boss is eager for Alexis to fire his country to South American glory.

"When Alexis is not in the fullness (of form) that he has us used to, Chile feel it," said Sampaoli.

"If he is feeling good, he's the most decisive player in this team. We must recover him well because he's vital to us."

Alexis had a stellar debut season in England, scoring 25 goals in all competitions for Arsenal, but has contributed just one goal for Chile in the Copa America which came in the 5-0 drubbing of Bolivia in the group stage.