The big mistake the Pirates made last off-season was that they relied too much on their young starting pitching prospects to provide an impact. They had Tyler Glasnow, Jameson Taillon, Chad Kuhl, Steven Brault, and Trevor Williams in the Triple-A rotation, with most of those guys expected to arrive in the middle of the 2016 season. As a result, they acquired lower upside guys for the rotation, trading for Jon Niese and signing Ryan Vogelsong and Juan Nicasio.
The plan didn't work. Every member of the rotation under-performed, which wasn't good for the off-season additions, as it took them from back of the rotation starters to guys who didn't look like they belonged in the majors as a starter.