I think his best contribution for us is essentially the same role he plays for Spain. Not a starter, because perhaps he doesn't have the influence or goals in him to make an impression the way Silva, Nasri or Jovetic can do, but perfect to bring on when we either need an outlet to counter if we're already winning, or chasing a result if we're not.
He has a lot of growing to do at City though. He may be a Spanish International but he's been in Sevilla his whole life. This is different football, in a different place. We'll have a better idea after a season.