To get this list, I eyeballed the Season 15-18 IFA's and drafts, pulled out what looked like the top 13, estimated their future ratings and plugged those into a spreadsheet I use to rank pitchers in amateur drafts.
What I learned from this look was that relief pitchers are about the only place you can regularly find draft or IFA bargains - the average position of the draftees was #15 (ranging from #2 to #32) and the average bonus for the IFA's was just $5.4MM (numbers for the 13 I evaluated). The 13 are also all really close - I'd love to have any - so the poll on who the top ones are should be interesting.
#1 - Chris Snyder (Sea 15 #18 overall, Austin - currently AA): best combination of vL and vR you're likely to see anywhere...put together with very good control, velocity, groundball and P1, and Austin has themselves a great closer for the next dozen seasons. His second pitch is only pretty good - the only flaw.
#2 - Zoltan Steinbach (Sea 15 #23 overall, Little Rock - currently AAA): just really good across the board - his worst rating is a vR of 75 (I'm not counting velocity as a rating that matters a lot, although it does affect strikeouts). Very good groundballer with excellent pitches...what a find for the Pebbles.
#3 - Wally Darwin (Sea 18 #2 overall, Toledo - currently Low A): The Mud Hens expended an awfully high draft choice on this guy but it might be justified (same with Browning, and both because they'll throw a ton of innings along with putting up quality numbers). Darwin projects to be a very high-control, command-type pitcher who's really tough on righty batters. One really good pitch and a good second pitch - the only very minor thing separating him from the top two is that he'll only be good - not great - against lefties.
#4 - Blaine Knight (Sea 15 #9 overall, Detroit - currently ML): excellent control, very good splits, keeps it down. Pitches: Excellent P1, OK P2, his third pitch is going to hurt him some.
#5 - Joseph Kida (Sea 16 IFA, Jacksonville - currently AAA): Power lefty with great control, will absolutely destroy lefties. Righties will have trouble, too, but will at least have a chance. P1 great, P2 pretty good. Will give up some longballs.
#6 - Roy Waters (Sea 18 #23 overall, Richmond - currently Low A): like #3 Darwin, this pick depends on development. I think Waters will improve well - he has good makeup and his vR in particular is already very high. At maturity, his ratings won't be as high across the board as the top - 5; his vR will likely make the 90's, but others will be in the 70's.
#7 - Derrick McFeeley (Sea 17 #32 overall, Oakland - currently Low A): great find at the end of the first round for the Surenos. Another soft-tosser who will have generally good ratings across the board...just lower than those of the top 5.
The best of the rest (no particular order):
Alexander Browning (Sea 17 #2 overall, Toledo - currently ML): that vR only gained 3 points in his second pro year, and looks like it will only reach low 60's. I think he'll still be good, but clearly righties are going to beat him up on occasion.
Yuniesky Jiminez (Sea 17 #10 overall, Scottsdale - currently AAA): pretty good overall; again, the vR is the real suspect. I think his will develop better than Browning's but his is starting pretty low.
Pete Prince (Sea 17 IFA, Ottawa - currently High A): outstanding bargain for a $2.6MM bonus. Won't have great splits but his pitches are already really good...and he has 2 more years of solid development to go.
Albert Dominguez (Sea 17 #16, Vancouver, currently AA): This is probably the guy who has a chance to jump into the top group. He's the extreme flyball pitcher of the bunch - I think he'll have some outstanding seasons but will always be plagued by homers.
Albert McMichael (Sea 16 #13 overall, Scranton - currently AAA): will be very solid...all his ratings are pretty decent for a ML pitcher now, and he has another solid year of improvement in front of him. Also will be susceptible to the longball.
Yovanni Velazquez (Sea 18 IFA, Pawtuckett - currently AAA): I had to throw in one crapshoot and this guy is it. I really have no idea what his projections are, but his groundball rating and first 2 pitches are already really good. If his splits develop at all, this guy could end up being a really nice closer. What do you want from a closer? Either a strikeout or nothing out of the infield. It's conceivable that this guy reaches 100 on both Vel and GB.