Quick takes on why the pitching could be underrated
1. The prospect folks tend to undervalue relief aces, I think.  They have good reasons, but real-life GMs view it differently. Does anyone notice that possibly 16% of our 25-man roster could stem from one single relief ace?  (As in: Guti, Vargas, Ryan [via Cleto] and Carp if he makes it)  And how reliable relievers are getting big money even if not closers?  (In other words, some guys may have "flip" value even if they aren't the kind that you, personally, would consider highly valuable -- like having stainless steel appliances and granite countertops in your kitchen.)
2. Lueke: "the baggage" combined with his "relief only" tag.  But he could be as valuable as anyone on the list including Ackley and Pineda in actual MLB games.  What he did on the field last year was amazing and not "smoke and mirrors" -- he brings the heat, doesn't walk people and keeps the ball in the yard.  What are you looking for in a relief ace?  It wasn't a K every three outs, it was a K every three batters.
3. Robles: the stature thing, and not going deep into games.  But Doc and G have some very compelling arguments that he's being undersold.
4. Wilhelmsen: a 26-year-old in A ball -- sure ticket to the cyber-equivalent of eye-rolling and a dismissive chuckle.  But if he'd gone to college and pitched the way he pitched in A ball at 19, he would have moved into the top couple of rounds (he was a 7th-round pick out of HS as it was).  And follow what the Z-crew did: Arizona Fall League, right onto the 40-man, and ticketed for AA (skipping High Desert).  And they get the full years of club control regardless of what age he is coming in.  I think the tools are real, and he's like a high draft pick that's a total freebie.
5. Paxton: obviously wasn't signed.  Churchill says he would have been #9.  That's fair, given the uncertainty (although Taijuan and Littlewood have plenty of uncertainty, too).  But also pretty much a freebie.
6. Moran: another one hard to evaluate on "traditional" ratings and "relief only" tag as well.  But the performance cannot be denied.  Like former Tar Heel teammate Seager: more "baseball" value than "prospect" value.  But the Z-crew is showing a knack for finding those kind of guys, and I think a lot of them are going to contribute as MLB role players.

There are two Guillermo Pimentels in the minors.  One was born in November 89 and is a member of the Rangers.  The other was born in October 92 and is ours.
You have the wrong on in the picture.  Maybe that's a joke I'm not in on. ;)  After all, we did sorta steal our Pimentel away and sequester him after he agreed originally to sign with the Rangers, and held him captive til he signed on the dotted line with us.
Basically true story, that.  We kept him away from all other teams until he reneged on his verbal deal with the Rangers and became a part of our org.
Still, Mariner, not Ranger, so could ya change the pic? :)
I've always loved this video of him at 16. http://vimeo.com/4803907
Uh...doesn't look like a 16 year old body or swing, but if he really is that age in the video then I understand giving him 2 million bucks and kidnapping him.
He started to drive the ball at the end of the AZL last year.  He was the #1 prospect in it for a reason.  If his eye comes around with more pro experience he's gonna be fun to watch.
I really hope he's got it in him.
As for THE worst pitching?  We should get to see some arms this year, even with Pineda's (and hopefully Lueke's) promotion. If the low-minors kids throw like I think they can it could be fun, even if there will be several of our best pitching prospects in the pen. 
~G