The Spaniard made the switch back in 2011 when he was just 16 years of age and has admitted, unsurprisingly, that the physical training in England was difficult to adapt too.
"We were blowing, we had no breath whatsoever [in early training sessions]," he told Arsenal Player.
"We were thinking 'what have we got ourselves into? This is not what we came here to do!" But then in the afternoon we played some football.
"That was what struck us the most though. When we were back at Barcelona everything was with the ball, even every single physical activity, it always involved the ball.