Well, to get a good idea about what was expected out of Cano, lets take a look at his yearly slash lines.
2005: .297/.320/.458
2006: .342/.365/.525
2007: .306/.353/.488
2008: .271/.305/.410
2009: .320/.352/.520
After a solid rookie year, he was fantastic in 2006, and while he took a slight step back in 2007, that could just be attributed to the natural progression of a young player. However, in 2008 he was extremely streaky, and if it wasn't for a hot start following the all star break those numbers would be even worse. In the list of Yankees' disappointments from 2008 Cano is near the top.
He seemed to alter his approach a bit, and he bounced back in 2009 with a really good year. I think there were more contributing factors to his resurgence in 2009 than the simple ebb and flow of a young player. Sending Melky down in 2008 likely told Cano that his spot is hardly a guarantee. I think they also began to really stress pitch selection and focus on defense with him.
Most people who watch Cano play agree that he has all the talent in the world. This is just my opinion, but when you consider the fact that he's entering his prime, that he seems a bit more mature based on things I've read, and all his talent offensively and defensively, I think he can be a top fifteen player in this game. This would mean, in my mind, eclipsing a .900 OPS and becoming a plus player defensively. With that kind of production at second base, combined with positive defensive contributions, you could begin to mention him in the same breath as Utley. Maybe that's a bit of a reach, but I've watched him play for five years now, and when you see all that talent, I can't help but hold on to lofty expectations.
EDIT: Spud, obviously expectations are purely subjective, and many people might hold Cano to vastly different standards than I do. I don't want to sound like these are the universal beliefs about Cano. This is just the way I see him. Hope this answered your question.
EDIT 2: I'm also assuming your post was about Cano, and not Chan Ho Park. Hope I'm right on that count lol.