Zabaleta revealed Hart was unhappy with the goal conceded against Everton but expects him to rediscover his best form.
The Argentinian said: "We saw him during the week a little bit down. We need him to come back again to his best.
"Sometimes it happens in football but that's why team-mates need to support all the players. He knows we're all behind him.
"Of course he's upset. It's really hard for any player when you know you're not doing well. He has a personality so he needs to show that he's coming back to his best. And I'm sure he will do because he's a great goalkeeper.
"We've seen him for a long time doing very well so that's why it's strange to see him like this."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball