I'm looking at Williams to have a 5.00+ ERA. Same with Milton, though obviously anything under 6.00 would mark improvement for him.
Claussen and Harang are wild cards. Chances are that both of them see their ERAs rise in 2006, but they do have some factors which could push it lower too.
Claussen's should rise because he didn't pitch as well as his ERA last season (4.63 component ERA compared to a 4.21 actual ERA). If he pitched the same in 2006 you'd expect the ERA to bubble northward. However, he's only thrown 239 big league innings so it's perfectly reasonable to expect he'll improve a bit. Now if only improves a little, you'd get pretty much what he delivered last year for ERA. The main thing he needs to do is cut down on the homers allowed. Claussen's at the crossroads. This is his chance to step up and be a better pitcher. I'm not as confident that he'll do it as I was that Harang would last year, but ST should give us a pretty good indication of whether he's ready to make a leap (or even a hop).
Harang's likely to see his ERA rise because he just had the best season of his career. It's common to experience a bit of a dropoff. Yet Harang's got that big frame of his, which he learned to rely on last season. He should be even stronger in the latter portion of the season in 2006 (he had a lower ERA post-All Star last season, but actually pitched better pre-All Star). He won't slip much if he does slip and a guy with his profile (big fella who throws a heavy fastball with good location) is the sort who can string good seasons together.
Though the real spot for pitching improvement on the team is likely to be the bullpen. Todd Coffey and Ryan Wagner were flat out unlucky last season. Also, if they had advanced through the minors a level per year, they'd be rookies in 2006. They're big kids with some stuff and even if you aren't particularly enthusiastic about them, they're easily the two best bets in the Reds' pitching corps to do a lot better in 2006.