ESPN's Keith Law (Insider only) has ranked the Pirates' farm system eighth best in the game.
For the Pirates to maintain this strong of a system with a low payroll and a highly competitive major league team is one of the more under-the-radar stories in the game over the past few years. They landed four players in the top 100 and could easily land six or seven next winter.
Of course, the Pirates' string of strong seasons has been driven in large part by Andrew McCutchen and by veteran acquisitions like Russell Martin, A.J. Burnett, Francisco Liriano, Mark Melancon and Jung-Ho Kang. Their farm system has been well regarded for awhile now, but with the very notable exceptions of Gerrit Cole and Gregory Polanco, a lot of the best young talent they've acquired in recent years is still in the minors.
Perhaps unsurprisingly, given their series of recent trades, the Braves rank first. The NL Central fares well overall, with the Cubs at No. 4 (despite the high-profile graduations of a number of top prospects), the Brewers at No. 5 (a massive improvement over where they were a year ago), the Reds at No. 12 (thanks in part to their recent deals, especially the Johnny Cueto trade) and the Cardinals at No. 19.