Revamped Bullpen The Key For Diamondbacks

David Hernandez of the Arizona Diamondbacks delivers a pitch against the Milwaukee Brewers at Chase Field in Phoenix, Arizona. Arizona won 4-0. (Photo by Norm Hall/Getty Images)

Arizona's bullpen, so terrible in 2010, has been central to their success in 2011.

The Diamondbacks are alone in first place in the National League West, and the headlines would have you believe it's been their high-powered offense and the strong pitching of their top two starters, Daniel Hudson and Ian Kennedy, that have propelled them to this point after losing 97 games last season. While there is no denying how much this rebound campaign from budding star Justin Upton has meant to the lineup, or how having Hudson for a full season rather than two months has helped change the rotation's fortunes after the departures of Dan Haren and Max Scherzer, there is another area that merits attention: the bullpen.

It's easy to overlook Arizona's relievers, as, except for David Hernandez and J.J. Putz -- both acquired by first-year D'backs general manager Kevin Towers -- there isn't anything impressive about the group. They have those two quality bullpen arms, and then a collection of relievers who aren't helping much, but aren't hurting them a whole lot, either.

But baseball is a game of relativity, and compared to the 2010 bullpen, the 2011 pen might as well be stocked with Mariano Rivera clones.

At the end of last year, I wrote at Baseball Prospectus, "Just a replacement-level effort in 2011 would increase the Diamondbacks' win total in the same way adding Mariano Rivera would." They finished with a bullpen three wins under replacement -- for comparison's sake, with about a month-and-a-half to go this season, not a single bullpen has even hit the -1 WARP mark.

By Baseball Prospectus's Fair Run Average, which measure's the effects of a pitcher's performance without giving him credit for the work of his defense, the Diamondbacks ranked last in 2010. They weren't satisfied with just finishing last, though: their 6.17 FRA put them further away from the Red Sox, who ranked 29th at 5.10, than Boston was from the fourth-ranked White Sox, who finished at 3.98. 

This year, though, they are better than replacement level -- nearly three wins better by WARP, in fact, putting them six wins ahead of last year's pen already -- and are right around the average. Their 4.35 reliever FRA has them tied for 14th in the majors, nearly two runs better than last year's performance. Again, the 2011 numbers aren't sexy, but they are a massive improvement. Think of it like this: for all attention paid the Diamondbacks' offense, they are scoring 0.18 more runs per game than they were last year. Yes, the run environment is lower this year (4.16 compared to last season's 4.33), but that's a small change that requires a decimal point to see the difference. The bullpen is almost two full runs better each nine innings they pitch, close to a run per game with their heavy workload.

Fixing the bullpen was the easy choice, because in order to actually rather than hypothetically score the equivalent of runs the Diamondbacks' pen has been saving, they would have needed two Jose Bautistas in the lineup. Since there's just the one and he's accounted for, Towers focused on trading for Hernandez and signing Putz.

Towers always had strong bullpens in San Diego, and often put them together on the cheap. The deals for both Heath Bell and Mike Adams comes to mind, as does trading Khalil Greene for Luke Gregerson. Towers' first order of business at the winter meetings was to give up Mark Reynolds for a pair of bullpen arms, including Hernandez. That price tag is a bit higher than we're used to seeing him pay, but he dealt from a position of strength (the offense) and acquired something the team desperately needed, and, as Hernandez has been their top reliever and is under control through 2015, and Reynolds' bat is offset to a degree by his poor glove, it may end up being worth the cost -- especially if they make it to October one year after losing almost 100 games.

The importance of a great bullpen can be overstated, as a strong rotation or powerful lineup can offset the lack of reliever depth. There is no overstating how much an awful bullpen can cost a team, though, as the 2010 Diamondbacks can attest to. It barely matters if your rotation can give you five or six strong innings if the bullpen is going to give it all back in their few frames a night, and that was something that needed to change if the Diamondbacks were to be relevant in 2011. With trade deadline acquisition Brad Ziegler now in tow -- he of the 63-percent career groundball rate -- the bullpen should only be better down the stretch, bridging that gap between the starter and another W in the standings that just didn't exist in Arizona last season. The result could be playoff baseball, but even if they don't make it that far, the reversal of the bullpen's fortunes has made for quality baseball in Arizona once more.

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