In 2013, the Pittsburgh Pirates bullpen was one of the best in baseball. They ranked in the top 5 in ERA (2.89), FIP (3.35), walk percentage (7.8%), and WHIP (1.17). They also were good in terms of xFIP (3.59) and SIERA (3.32).
This pen was led by extremely strong seasons from Jason Grilli, Mark Melancon, Tony Watson, and Justin Wilson. But one of the arms who provided many innings out of the pen, and was fairly underrated during this season was right handed pitcher Vin Mazzaro.