Hart's performances have been questioned of late, including after his side's 3-1 Champions League defeat to Bayern Munich on Wednesday, and manager Manuel Pellegrini has refused to confirm whether he will start between the posts in the clash with Everton on Saturday.
However, England boss Roy Hodgson has confirmed that Hart remains his first choice, and the 26-year-old is still number one in Zabaleta's eyes too, with City's vice-captain insisting that almost every player suffers a dip in form.
"He's still the best. Right now is not his best moment but this happens," Zabaleta told BBC Sport.
"Sometimes Joe Hart, like any player, can make a mistake. Everyone makes mistakes. It is impossible to be at the top level for 60 games a season over many years. Maybe sometimes [Lionel] Messi or Cristiano Ronaldo do it.
"But I've known Joe Hart for five years and have seen him playing at his best form and know that he is the best. The feeling for me and my team-mates is that, looking at him in the goal, I feel safe."
Costel Pantilimon is on standby if Hart, who has started 120 consecutive Premier League games for City since returning from his breakthrough loan spell at Birmingham City in 2010, is dropped this weekend.