The 24-year-old struggled at Camp Nou last season, but has impressed in the early stages of the new campaign.
"The confidence for a player is everything. If there is confidence provided on the pitch, a player can do many things," Sanchez told reporters at a press conference.
"I feel really good this year, very comfortable and confident. Tata Martino gives me an amazing confidence that allows me to be more free on the field."
Sanchez is currently on international duty with Chile.