The former Real Madrid midfielder signed for the Gunners in a club record £42 million deal.
"I would have come here without a fee, that wouldn't have been a problem," he said.
"Of course I am proud of this (being Arsenal's record signing), but the most important thing for me is that the manager trusts me, that I can get trust from him.
"This was the crucial point for me and this is why I have come here."
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