Fitz did well with Warner and McCown last year, and Leinart is perhaps the most NFL-ready QB to come out of the draft in years, so I really don't care who is throwing him the ball. The problem would be if that defense gets a lot better, and the Cardinals start playing with the lead too often, but I doubt that's going to happen either. They're still a year away from being a serious contender.
Being that he's easiyl just as talented as Boldin, and Denny Green's favorite adopted son, I'm willing to bet Fitz has a huge role in that offense. Plus, he's been able to stay healthier than Boldin, who I also think will have a great fantasy year, hence I'd rank Fitz at least the #3 WR in any scoring format.