In terms of under the radar, I think you are a year too late on Tracy. On the strength of BaseballProspectus last year, I made him a late round pick in my 2005 draft and was VERY happy with his performance. I don't think he'll be available in round 22 in 2006--that's where I got him.
This year, I'd expect more of the same to a slight decline. This was towards the top end of what I think he was capable of doing. Here's what Baseball Primer's projecting for 2006:
Name P AVG OBP SLG G AB R H 2B 3B HR RBI BB K SB CS
Tracy* 3b .294 .349 .460 148 530 69 156 31 3 17 70 43 64 2 2
I think that's a little on the low side.
I'd expect something like: .300/.350/.500 for BA/OBP/SLG with 75 R and RBIs and 23 HRs.
One concern may be the the D'backs have some excellent prospects, so Tracy could be traded or could lose PT if he slumps.