It's pretty important to find written information about prospects rather than just meaningless rankings. Guys ranked outside of the top 50 this year can easily become top ten guys next year because everyone knew they had the ability, but the results weren't there yet. To figure out starters who can make an immediate fantasy impact, finding pitchers with polished, well-rounded repertoires (see Tim Lincecum) rather than guys who just blew away the inferior competition based off the dominance of one or two pitches (see Andrew Miller) is pretty important. You can also figure out pitchers who were downgraded because of injuries but are primed for a major leap like Jordan Walden, a guy who was projected as an ace, mysteriously lost his velocity and has now gotten it back and could shoot into the top 25 with a nice showing in '08
Here are the blurbs from the 2007 FBC Prospect Rankings for Clay and Joba, with neither guy being ranked in the top 50:
51. Clay Buchholz (SP-Bos) Buchholz had a breakout year in 2006, doing wonders to put aside questions regarding his experience. While typically throwing in the low-90’s, Buchholz hit as high as 97 mph when he received the call up to high-A Wilmington. His repertoire also includes a solid curveball and a change-up. Perhaps the best thing about Buchholz: his arm has not sustained much wear and tear, as he is still relatively new to pitching. The Red Sox won’t rush Buchholz, but if he keeps pitching like he has been, he could be called up to Boston in late 2008 or early 2009.
64. Joba Chamberlain (SP-NYA) A Native American out of Nebraska, Chamberlain has battled weight issues his entire life. This has led to his Nebraska nickname “Joba the Hut”. On the field, Chamberlain features a mid 90s fastball, a slider, and a change-up, but it’s his curveball that may be his best pitch. Injury concerns may hurt his ranking, as in the past year he has had both knee surgery and elbow tendonitis. However, if healthy, Chamberlain should start the season in high Single-A ball, and advance quickly.
People here played up that Clay's repertoire was pretty established and if he proved it, he'd be gold. Joba was ranked lower due to injury concerns but he's hyped as a well rounded pitcher who would burst out if he stays healthy.
Andrew Miller was generally a top 15 prospect but struggled because he was a two pitch starter with weak command, like the scouting reports stated:
John Sickels in 2007 Preseason wrote:Andrew Miller: Andrew Miller is 6-6, 210 pounds, born May 21, 1985. He has been healthy and durable throughout his college career. Some scouts don't like his delivery and worry that he stresses his arm a bit much, but so far it hasn't been a real problem. His fastball is outstanding for a lefthander at 92-94 MPH, hitting 97 at times, with plus sinking action. His slider is outstanding. His changeup is mediocre and will need to be improved, but he's got the aptitude to pick it up with more experience. He has all the physical tools needed to be a dominant starter at the major league level, provided he refines his command a bit more.
Mike Pelfrey was also highly rated last year and struggled because he only had a fastball that could get major league hitters out.
Obviously, Miller and Pelfrey can still become nice starters but you can improve your chances at picking out the guys not ranked in the top 50 who have a great chance at moving up by reading about them and deciding whether or not they dominate the minors off the strength of one or two amazing pitches with spotty command or have the polish needed to get MLB hitters out relatively soon.
I got into prospects when I kept getting burned in my keeper league by other managers getting those rookie gems like Braun and Lincecum and in my ignorance, I dropped Cole Hamels from my minors system (only 3 guys each) because he kept getting hurt and I didn't think he'd ever be that successful. I picked up CB Young for him so it wasn't a complete loss but colossal mistakes like that will make you wake up. Now that I pay much closer attention, I have guys like CB Young and Joba Chamberlain on my team and others like Colby Rasmus waiting in the wings rather than wasting time on busts like Jeff Mathis.