From 2012-2014 fans pretty much knew what to expect from Zack Cozart. He was going to be an incredibly good defensive player and struggle at the plate. The numbers bear this conclusion out. From 2012 to 2014 Cozart, at his best, was 17% worse than a league average hitter. At his worst he was 45% worse (2014). These numbers are based on Fangraphs' wRC+ statistic.
However, even with those offensive struggles Cozart was still a 1-2 win player for Cincinnati because of his defense. In 2014, his worst offensive season, he ranked as the second best shortstop in baseball by DRS (19), and the third best shortstop by UZR (12.