The 25-year-old, who has started all four of Barcelona's Primera Division matches this season, insists he is still up for the fight.
"I said when I signed here that it was going to be the most exciting and difficult challenge of my life," he told The Sun.
"I knew I was coming here to compete for a place against the best players in the world.
"But I like big challenges. If I didn't, I would have stayed at Arsenal where I was the captain, where I played every game and where I was treated so well.
"I would never have taken the big step and the huge risk to sign for Barca and fight with the best players in the world for a place in the team - especially as there were never any guarantees given that I would play.
"I have a big heart, I have a strong character and I have the courage to carry on competing for my place."