Per Mertesacker has backed Petr Cech to be "even stronger" after making a string of errors on his Premier League debut for Arsenal.
The goalkeeper, who joined the Gunners from Chelsea earlier this summer, let in two goals against West Ham United, before looking more settled in the win over Crystal Palace on Sunday.
The defender told reporters: "Petr is very experienced. You can feel that, he has lots of things to say and in the dressing room he gives us a great lift. Even when we lose a game, he has some great ideas on and off the pitch. He is experienced enough to think about what went wrong, you don't have to tell him.
"My feeling is he comes back even stronger, so there is no doubt he will be a great addition for us. Even when you are experienced, sometimes mistakes happen.
"The interaction between the goalkeeper and the back four has to be top to compete in the Premier League. Sometimes it takes longer than you think. Petr came and had that understanding from the start, we both communicate well and understand each other as someone who has to talk and is really responsible."
Arsenal host Liverpool in the Premier League next Monday.
