Evaluating Arizona’s Remade Bullpen

There’s no charitable way to describe the performance of the Arizona bullpen last year. The group combined to finish last in MLB in ERA (5.74), xFIP (4.69), HR/9 (1.3), WAR (-2.1) and WPA (-8.37) and in the bottom five teams in K/9 (6.8) BB/9 (4.6) and innings pitched (439). They were awful. So as soon as he became the Diamondbacks' GM, Kevin Towers vowed to make changes.

“The focus will probably be primarily on the bullpen this winter, as well as the bench,” Towers told reporters in September.

We’re nearly a quarter of the way through the season, and while it’s too early to make sweeping conclusions about Towers’ work, there’s a distinct sense that the ‘pen is much improved. So far, D’Backs relievers are 3rd in MLB in K/9 (8.7), 7th in BB/9 (3.3), 15th in ERA (3.26) and 4th in xFIP (3.45).

David Hernandez, acquired in the Mark Reynolds trade, has been an asset, though he still hasn't limited his walks. Towers' big offseason splash, J.J. Putz, has provided the D'Backs with a stable late-inning presence (while his former White Sox teammates have been anything but in Chicago). And Rule 5 pick Joe Paterson has yet to allow a run in 15 carefully-timed appearances as a lefty specialist and has struck out more than a batter per inning.

Paterson hasn’t cost Arizona more than $50K and a roster spot, but the other pieces in Arizona’s ‘pen were significantly more expensive in terms of cash and Major League talent. The D’Backs gave up their starting third baseman to acquire Hernandez and Kameron Mickolio (though they seemed more than ready to part with Reynolds and his strikeouts). Of the $20.5MM Towers spent on Major League free agents last winter, more than half – $12MM – went to relievers Putz and Aaron Heilman. 

As a result of Towers’ offseason moves, the bullpen has been more than passable. The team’s starters, however, are 28th in baseball with a 4.91 ERA and Arizona is 15-20. Though the D’Backs have not caught up to the Giants and Rockies overall, they do have a significantly better bullpen in 2011.

Click here for analysis of the Rays' and Padres' bullpens.