Hernandez, who joined Real on a season-long loan from Manchester United on transfer deadline day, scored his first goals for the Spanish giants with a late brace in their 8-2 hammering of Deportivo La Coruna on Saturday.
And his fellow Mexican Sanchez, a Real legend who scored 208 goals in 282 matches for the club between 1985 and 1992, believes that Hernandez will go on and net many more in the famous white strip while playing alongside the likes of Cristiano Ronaldo, Gareth Bale and James Rodriguez.
"He scored two great goals and I'm sure he will score many in Madrid," Sanchez told AS. "He's a phenomenon.
"[He is] very fast, intuitive, with movement and speed and he shoots well with his left and his right and his head.
"He is a player who intercepts the opponent very well and visualises what's happening next. What he needs to win a place under [Real coach] Carlo Ancelotti is what he did at Riazor. Confidence comes with goals.
"When he's given more time and more chances, hopefully he will be as effective as is required in Madrid.
"In this team there are enough chances created and that will help."
