The Chilean has struggled this season.
"Everybody in Chile feels that he is an extraordinary player and believes he will resurface again at some point," Zamorano told Marca.
"Alexis is a great player who always does his utmost for the team. He will never let down his team-mates or not give his all. Every player goes through a difficult period at some point in his career.
"I went through a similar slump during my time at Real Madrid. I failed to find the net for three months or so. And I was a striker, whereas Alexis generally acts on the wing."