Going back to GC's earlier point about players having reputations, take David West.
West has a reputation of being a pretty poor defender, despite the Hornets being a pretty good defensive team. However, last season, that reputation was completely unfair. West ranked 70th in the entire NBA for points allowed per possession, at .82. That's an excellent number. He was very good against the P&R and in the post in particular, and overall, he allowed opponents to shoot 37.4% against him (and 37.4% on post-ups, as well).
In other words, not only was David West not a poor defender last year, but in fact he was a very, very good one. I think that bodes very well for Philly's chances this year.