The midfielder joined the Gunners from Everton for £10m during the final hours of the summer transfer window, and he has said that the tight time restrictions meant that the North London club had to trust his word that he was fit.
"It was very stressful," he said. "At 6pm, they said everything had broken down. Then, at 8.30pm, everything started again.
"But there wasn't time to have a medical. I went to the offices of [Everton] and from there I told Arsenal to trust me and that if some medical problem was found it would be my responsibility."
The Spaniard was sidelined for nearly 12 months after he suffered a serious knee injury in February 2009.