Former Arsenal goalkeeper Jens Lehmann says he was surprised by Petr Cech's disappointing start to the Premier League campaign.
The Czech international made two mistakes in West Ham United's win over the Gunners at the Emirates last week.
But Lehmann is convinced that the 33-year-old will bounce back and be a key element in Arsenal's fight for the Premier League crown.
"It surprised me [his performance against West Ham United] because I expected him to be really good from the beginning," Lehmann told Goal.
"But sometimes it takes a while to adapt to a new club, particularly when you are coming from a major enemy like Chelsea. It takes time, if he can forget about it at all.
"On the other hand, Chelsea disappointed him because he couldn't play there last season. He has seen the cruelty in football - you are a hero one year and the next year you are not even playing any more.
"That could spur him on to play a fantastic season for Arsenal.
"He is the goalkeeper Arsenal need to win the title.
"He's got the experience, he's got most of the ingredients that a fantastic goalkeeper needs and he is among the best ever goalkeepers.
"It depends on him. I haven't spoken to him, so I don't know how he feels physically now, but I think he's still got some great years to perform at this level. He will give confidence to the whole team, but of course he has to perform."