There were many factors in the Pirates’ failure to reach the playoffs last season, but the biggest was that their pitching rotation simply wasn't good enough.
Jon Niese, Juan Nicasio and Jeff Locke were three of their five starters, and that alone eliminated them as a playoff contender. Gerrit Cole and Francisco Liriano struggled, which didn't help, but they couldn't have pitched well enough to carry the Pirates to the playoffs, given the back end of their rotation. Niese and Locke are gone, and Nicasio is in the bullpen, so the Pirates have a chance to upgrade their rotation.