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Fan Confidence: Has the Bullpen Been Overused?

People thought the bullpen would be a strength for the Diamondbacks in 2013, yet there have been some noticeable miscues and blown opportunities. We look to see if overuse might be contributing to the malaise.


I speculated in Sunday's video chat that part of the bullpen's recent issues could stem from overuse, which is part of a larger problem. The specific line of thinking being that the offense isn't scoring enough, and the starters aren't going deep enough, forcing Gibby to call upon his bullpen to keep things close with the hopes they can pull out a win.

As I'm wont to do, though, I made the statement merely in a speculative manner. It did get me thinking, though, whether the bullpen was being overused. It certainly feels that way, but would the data support the point?

I took a look at our bullpen's usage this year, and compared it to each reliever's average numbers over the past 3 years (or 2 for Collmenter). The categories I chose were:

  1. Appearance rate, which gives how many games on average pass between outings for each reliever
  2. Innings per appearance, which shows how many outs they work
  3. Pitches per appearance, which shows how much they're working per appearance

The idea here being that if my admittedly hasty hypothesis has any weight, we should see a difference between these numbers in 2013 and their average over the past 3 years.


Okay, so that was bigger when I created it, but if you get out your microscope you'll see that there has been an uptick in use even in just the one month in the books.

J.J. Putz has been used more, but not as much as Big Z. Brad Ziegler has been used at a much higher rate per game, to the point it might be alarming. Matt Reynolds, David Hernandez, and Tony Sipp all have seen their rests between games on average go down as well.

Putz and Hernandez have both seen in an increase in the amount of pitches needed, which can exasperate fatigue and bad outings. On the hand, Ziegler has need a fewer pitches in his outings.

Is this significant, though? Most of these rates have fairly minimal changes between 2013 and their 3 year average, so who cares? Well, assuming these trends continue, these rates could be fairly significant has time passes. For instance, if Ziegler continues to be used ever 1.72 games, then he's going to make a 94 appearances. So even though he's using less pitches per outing, it's probably not enough to balance the abuse his arm will take.

Likewise, Putz could make 68 appearances if his rate continues. I don't think anyone wants to see that happen, and I don't think his arm would hold out, especially since he's needed more pitches each outing. The danger here is that he doesn't make it 68 not because the appearance rate changes, but because his arm becomes a floppy, useless appendage.

There's no specific reason to believe these trends will continue, but it is worth concern. It could just be a rough month and things will settle down. But if the starters don't go longer, and the offense doesn't keep up, then the team is going to need to start getting creative with how they use guys so they don't break down.