LOL, you remember poorly. In 2007 I think he played one half in the first game against Mexico, which they lost 3:0. Throughout the tournament he didn't play at all, supposedly tired from the club season.
Absolutely, no one expects him to perform from day one. But his first season needs to be succesful. We can't wait for him 2 years, when we payed that kind of money.
I'm sorry but expectations for a 30€ mil signing, can't be kept low, or reasonable. There will be huge pressure on Diego and it will be on him to deliver.