I disagree with Hollinger's skepticism regarding our ability to maintain a top 3 defense. The defection of Thibs and Frank should have very little effect on the defensive effectiveness of the starting 5.
As long as KG and to a lesser extent Rondo are healthy our defense will be sterling. If JO is actually healthy this season, it's probably improved.
Offensively, I agree we'll be as mediocre as we were last season. The offensive upgrade from Baby to Bass/Wilcox is big, we won't have Shaq's brilliant quarter season this time around and I'd expect a small decline in minutes and/or efficiency from the big 3.
In my mind, our contention hopes rely on health above all (not only will we need to have our guys fully healthy, we might need our opposition to be a little beat up), and we'll need an extra boost via midseason pick-ups (Joel Przybilla, Kenyon Martin) and/or trade deadline moves for a bench scorer/playmaker (Leandro Barbosa, Mo Williams, Louis Williams, Grant Hill, Boris Diaw)