By itself, it’s not concerning that the system has dropped in the rankings (BA had them 7th a year ago). These things are cyclical, as shown by the Cubs, who dropped all the way to 28th thanks to graduations and trades. After graduating Jameson Taillon in 2016, the Pirates graduated Tyler Glasnow, Josh Bell and Steven Brault (yes, BA had him 7th in the system a year ago) in 2017. In fact, it’s a little surprising the Pirates didn’t drop further, with Austin Meadows having a disastrous season, Kevin Newman having a mildly disappointing one, and Will Craig remaining Will Craig.
The real problem for the Pirates is occurring at what, more and more, seems to be the truly critical and most difficult stage of the process: Getting the prospects to the point where they contribute in the majors. That obviously was a major issue with Glasnow and Meadows, who was expected to reach the majors in 2017 but didn’t get there at all. That clearly hasn’t been an issue with the Cubs, who’ve gotten much more value out of their system in the last few years than the Pirates despite having an average BA ranking from 2013-17 of just 11th, compared to the Pirates’ 7th.
You can argue that these ranking really don’t have that close a connection to major league success. The Cardinals are an especially good example. Their system has arguably been even more productive than the Cubs’ in the last few years despite an average ranking of 10th from 2013-17. (This year, BA ranks them 13th, with the Brewers and Reds also ahead of the Pirates at 11th and 9th, respectively.) I don’t really know what accounts for this, although I still tend to think it has less to do with coaching than it does amateur scouting and a willingness to give opportunities to rookies. The problem with the rankings is that they’re simply of limited usefulness.