Gallas said: “I am a good friend of Thierry so I wasn’t surprised when he went because I speak to him all the time.
“It was his decision to go and no one can question that. Everyone knows what a great player he is and what a good job he did for Arsenal.
“I hope he will be happy with Barcelona — but now he has left and we have to move on.
“We have to prove we can play without him and I am very confident the players we have at Arsenal are good enough to replace him.
“There has been a lot of talk about Tottenham and other teams finishing above Arsenal this season . . . well, we’ll see about that.
“Tottenham want to finish above us and we will do everything to make sure that does not happen.
“But our aim is not to finish above Tottenham. It is to finish in front of everyone and win the title.”