Barton has already impressed young Marseille player Billel Omrani.
"Prior to his arrival, we were afraid of his bad boy reputation, but to know him and seeing him everyday, he is a cool guy," said Omrani.
"This is very exciting, he wants to prove we can trust him and he can play with us. He is a fighter, it is not for nothing that he was captain of QPR.
"He will show his skill, he is often in the gym, on the field he talks a lot, this is an excellent player. He impresses me a lot."