Here's an article on Joshua Sharpless, a reliever who didn't give up an earned run all year at Class A+ Lynchburg before his recent promotion to Altoona. He struck out 48 in 28.3 innings.
I'd been watching Sharpless' stats with both excitement and anxiety - I'm glad to see he's been promoted, as it appears that the Pirates view him as a prospect. (Perhaps WTM can comment on whether that's actually the case or not.) The Littlefield Pirates have tended to leave older players (Sharpless is already 24, not 23 as reported in the article) they don't view as prospects in Lynchburg and Hickory in order to dominate the competition - think Adam Boeve, Jon Benick, Brad Rea, and so on. Forgetting about Boeve or Benick probably wouldn't come back to bite the Pirates, but someone like Sharpless might be another story - he's the sort of player who might get taken in the Rule 5 draft, and it wouldn't be hard to imagine him having success in the majors right away, either.