One of the best ways to figure out when (or if) a player is going to be promoted is by looking at what the organization has done with previous players. For the most part, each player is an individual circumstance and should be treated with an individual approach. However, there are usually a lot of trends you can find with an individual team which can be used to predict the path of future players.
For example, the Pirates have established a trend with their prep pitchers out of the draft. Most of them spend their first full season in extended Spring Training, then go to the New York-Penn League. The following season they make the jump to full season ball, spending the entire year in West Virginia. From there, we don't have a lot of precedent, mostly because the 2009 prep pitchers are the only ones who would have had a chance to move beyond the next step. We know the next step is Bradenton, but we don't know if a promotion is in line.
Tim is the owner and editor in chief of Pirates Prospects. He started the site in January 2009, and turned it into his full time job during the 2011 season. Prior to starting Pirates Prospects, Tim worked with AccuScore.com, providing MLB, NHL, and NFL coverage to various national media outlets, including ESPN Insider, USA Today, Yahoo Sports, and the Wall Street Journal. He also writes the annual Prospect Guide, which is sold through the site. Tim lives in Bradenton, where he provides live coverage all year of Spring Training, mini camp, instructs, the Bradenton Marauders, and the GCL Pirates.