The former Arsenal and Manchester City midfielder has been training with West Ham in the hope of securing a contract. Nasri is a free agent and is currently serving an 18-month doping ban that expires on January 1.
And Zabaleta believes Nasri just needs time in order to improve his fitness.
“Manuel knows Samir very well from his time at Manchester City,” Zabaleta told Sky Sports ahead of the Hammers’ home fixture with the Premier League champions on Saturday.
“We need players with his quality, especially because also we lost two key players who brought quality into this team – Manuel Lanzini in the summer before the World Cup and then [Jack] Wilshere, who is very close to coming back to the team.
“On the ball [Nasri] is fantastic. He is one of those players who can give to the team some possession and play between the lines to help the attacking players to create chances.
“Samir needs a bit of time. He has not been football training for more than a year but sometimes those players are technically very good so he probably needs to focus more on his fitness levels than his passing and all this.
“We know Samir and his quality. When he is fit he is on a different level. He is a fantastic player.
“Hopefully he can reach his best fitness level. He has to feel physically good because we know that the Premier League is so demanding physically.”