What makes you think that?
When he played for arsenal, especially at the end, I always thought he looked like he was playing for himself. He was very lazy when they didn't have the ball, seemed to just run wherever he wanted to when they had it, except with a view to creating space for someone else. They always looked really dodgy when he was in midfield. He made bad decisions throughout most games. I was disappointed when they sold him because I thought they might start winning things again!
Maybe he's different for Barca though.