The Giants have a nasty schedule this year, and Eli's problems will become clearer against them. He makes the occasional bad decision or just a plain bad throw, and teams will pick him off. The thing is, against their stronger schedule, those teams are going to be better at exploiting this weakness.
Teams w/ tough secondaries to play include: Philly, Seattle, Dallas, Tampa, Chicago, Jacksonville, Carolina...arguably Washington, if Shawn Springs is healthy. Those teams are 11 games on his docket this year.
Expect a junior slump from the junior Manning, although I think he bounces back for a good year next year.