I looked at the projections for D Backs hitters and pitchers currently projected to be on the 25 man roster. The projections are from 5 different sources:
Pecota, from baseball prospectus
ZIPS, from Baseball thing Factory
Bill James, from the Bill James Handbook
CHONE, from Sean Smith
Marcel, from Tom Tango
These are all 5 very respected sources in the statistical community. They don't agree on all players. On some there is quite a large range of projected performance. For example, for Justin Upton the most pessimistic projection is .717 OPS and the most optimistic is .849. For others, the projected range is actually quite close. Not surprisingly, the more at bats the player has, the closer the range tends to be, for example, for Byrnes the range is 770-810 and for Hudson the range is 780-820
What I did was simply take the AVERAGE of the 5 projection systems to get a rough idea for a "group" projection average. I'm just showing OPS and ERA to keep it simple
OPS First. Keep in mind ballpark adjusted league avg OPS for Chase Field last year was .797 and team wide OPS was just .734. So the projected numbers below would be a clear improvement to the team offense
Jackson .845 (.835 in 2007)
Reynolds .838 (.844)
Tracy .837 (.800)
Young .816 (.762)
Hudson .792 (.817)
Byrnes .790 (.813)
Upton .781 (.647)
Montero .770 (.689)
Salazar .768 (.734)
Drew .763 (.683)
Snyder .755 (.775)
Burke .728 (.661 with Houston)
Ojeda .670 (.708)
ERA Projections:
Webb 3.33 (3.01 in 2007)
Haren 3.76 (3.07 with Oakland)
Qualls 3.87 (3.05 with Houston)
Cruz 3.88 (3.10)
Pena 3.91 (3.27)
Slaten 3.94 (2.72)
Johnson 4.05 (3.81)
Lyon 4.10 (2.68)
Owings 4.49 (4.30)
Davis 4.61 (4.25)
Gonzalez 4.66 (5.03)
Nippert 4.79 (5.56)
Those ERA's may seem high to some, but actually that would probably yield a team ERA as good or better than last years 4.13