The midfield whiz said: "Gaby is going to contribute to the team very important things with his football characteristics, he is going to reinforce the defence of Barcelona.
"I am very happy with this signing. He is a great player, a winner."
Asked about Diego Maradona's demands that he be given the No10 shirt of Argentina, Messi added: "I cannot be more grateful to him and will continue thanking him for everything he says about me.
"He is the greatest of all and he always supports me. It would be nice if they gave me the No10, but I do not give much importance to a number, sincerely for me they're all the same.
"The only thing I want is to be always in the national team."