The Frenchman joined Premier League champions Manchester City on a Bosman this summer after failing to negotiate a new contract with the Gunners.
"Looking at it on paper I think it is the strongest side we have had. Except for obviously Thomas [Vermaelen, who has moved to Barcelona] we have not lost any key players," he told reporters
"Even if someone did leave on a free contract we managed to replace them with good players. So we are looking stronger and stronger and we are very happy with that.
"Calum is really solid, he is only 19 as well. And Mathieu has a lot of experience so we hope to see him perform at that level all the time."
Arsenal begin their Premier League campaign by hosting Crystal Palace at the Emirates Stadium on Saturday.