Despite saying that the 25-year-old forward still has plenty of improving to do for both club and country, Sampaoli claims that the number of star players with the Catalan giants makes it difficult for Sanchez to make the desired impact.
"With Chile, Alexis knows he is a decisive player," the Chile boss told reporters. "He is very highly thought of - a superlative player.
"Perhaps at Barcelona, with the team-mates he has and all the great players there, it is more difficult, but for me he has all the conditions to be one of the best players in the world: assists, goals, dribbles, everything.
"He can still get much better than he is at the moment and he'll be one of the key players in club and international football over the coming years."
Chile face Brazil in the last 16 of the World Cup on Saturday.