You can see the list here. The Pirates have a startling number of minor league free agents.
The reason this is significant is that - and someone please correct me if I'm wrong here - with a couple of exceptions like the Rule 5 draft, a team controls the minor leaguers it drafts for six years. After that, they have to be added to the 40-man roster, or they become free agents. This means that minor league free agents are players who either lasted six (or, sometimes, seven) years in the minors and just didn't stick, or veteran journeymen who've been around for a very long time and were signed to short-term deals to fill spots.
There are some washed-out former prospects on the list of Pirates, like Antonio Sucre, Ray Sadler, Landon Jacobsen and Mike Connolly, but the overwhelming majority of the Pirates on this list are just veteran space-fillers. If a team has to sign a ton of minor league journeymen, it means that, for whatever reason, it can't even get many of its draft picks to contribute at the minor league level, let alone at the major league level. Not only does the presence of all these minor league journeymen suggest that the Pirates's drafting and developing personnel just aren't getting the job done, but also that they're wasting money: it's more expensive to sign a minor-league journeyman than to just fill that spot with someone you already control.
Twenty-three members of the 2006 Altoona Curve are now minor league free agents. The Curve was the only Pirates affiliate to make the playoffs.
Is there anyone left who still thinks the Pirates have a good minor league system?