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The Arizona Diamondbacks bullpen is better than you think

The offense is making them look bad!

MLB: Arizona Diamondbacks at Colorado Rockies Ron Chenoy-USA TODAY Sports

“Better than you think” is a relative, and admittedly loaded term. However I don’t think it’s a stretch to say that most D-Backs fans and followers do not have a favorable impression of the bullpen.

At the same time it’s likely most people look at the offense as having been a strength of the team, and on a macro level, they are correct. Most would be inclined to lay the majority of fault for the team’s 13-19 record in one run games, 6thworst in MLB and only better than the Marlins in the NL, squarely at the feet of the bullpen members and Torey Lovullo’s bullpen management.

Until I started researching this article, I was inclined to agree. And in fact one would not need to search very far or long to see numerous comments from me lamenting the declining stuff of Greg Holland, or Archie Bradley’s string straight fastball, or Yoshi Hirano’s lack of command on his splitter this year. (I also personally volunteered to drive Matt Koch to the airport back in April)

So what’s with this article headline? Let’s go!

*Note: All Ranks are NL only. The bullpen is a different animal in the NL, what with no DH, and managing around the pitcher’s spot in the order.


Ok, so we start here. fWAR is based on FIP, or fielding independent pitching. It uses Walks, Strikeouts, and Homeruns to isolate the things that are simply not dependent on the quality of defense behind the pitcher. The measure is then converted to an ERA like number for easy understanding.

RA-9 WAR is the opposite. It is based on ALL runs allowed per 9 innings, regardless of earned or unearned. In both measures, the DBacks are above league average but rank squarely middle of the pack.

Link to NL Bullpen Value Page

OK, WAR isn’t everybody’s cup of tea, and it’s just a starting point for discussion, not an end point. Moving on.


So here we have traditional ERA, and I also include FIP, explained above. xFIP is similar to FIP, except it “neutralizes” homeruns. The assumption being that HR per Fly Ball rate is not always something a pitcher can control either. While that does not seem intuitively correct for many of us, there is enough basis in the data to make it a reference point worth checking. (As always with these things, look for outliers and extremes.)

The “minus” stats are League and Park adjusted measures. 100 = League avg. Note for NL league avg. is over 100 , but it’s lower than 100 in the AL, mostly due to the DH.

Here once again, we can see the D-backs bullpen is squarely in the middle of the pack when it comes to overall run prevention. Almost exactly league average.

NL Run Prevention Table, Ranked by Bullpen ERA

If you haven’t yet, you’ll want to start clicking through on some of these links. Be sure to see which teams are at the bottom and the top of these tables.

Ok, you say, they may have league average ERA and FIP and whatnot, but surely they have stunk when it mattered most, right ?


Wait, what ?!?!. Yes, your eyes are not tricking you. The above table is telling you that the Dbacks bullpen, as a group, and for the entire season, has been WELL above average in situational and high leverage.

You’ve seen me talk about the inherited runners scored %, and seen it from the broadcast booth several times. The D-backs have far and away the best % in MLB. As an aside, Andrew Chafin has the 2nd most Inherited Runners faced of any reliever in MLB (34) and only allowed 3 of them to score. LINK

Their Batting Avg w/RISP ranks 3rd best in the league, as does their WPA (Win percentage added). WPA measures the difference in win expectancy of each Plate Appearance . This is highlighted at the end of every game recap on this website. Here again, the D-backs pen is among the best in the NL. Shut Down/Melt Downs are included for those that like that measure better than WPA.

And then we come to simply high leverage ERA. Note how high that number is for the league. When there are runners on base late in close ballgames, they tend to score. Every team’s number is high in those situations. But the D-Backs have the 2nd best ERA in High Leverage Situations in the league. They are actually a little worse than average in Medium and Low Leverage situations.

I would be remiss to not point out that they have not been as good in High Leverage since the first month of the season, but they are still better than league average over the last five weeks by over two runs.


The objective evidence clearly indicates that the Diamondbacks bullpen has been at least league average in overall run prevention, and has actually been well above league average in situational, high leverage situations.

One area that probably makes us feel like we don’t have a “lights out” bullpen is also the fact there are only a couple of hard throwers, (Bradley and Lopez). Most of the other guys have below average velocity for a reliever. In fact, they have the slowest velocity in the league. But clearly that has not kept them from being effective most of the time.


So why is the one run record so lousy? For the most part, these are low scoring games. The D-backs have averaged 3.84 R/G in one run games and allowed 4.03 R/G. A couple more big hits in some of these games would have gone a long way to helping that one run record.

In fact, the D-Backs offense has been pretty bad in high leverage situations, especially very late in games. And that has put an inordinate amount of pressure on the bullpen. Here comes the money shot.

I’m not even bothering with the color coding. It’s really bad across the board. Notably, the other team that is equally bad in these situations are the Reds, who are the only team to underperform their run differential/pythagorean won loss more than the D-Backs. LINK

League Batting Table Links

One last statistical note: The D-Backs actually rank 2nd in NL in total BA W/RISP, (.272) but as can be seen above, it’s quite poor in high leverage. (.223) In medium leverage it’s .266, and in Low Leverage it’s a whopping .306.

The offense has done a good job of piling on when they get it going, hence their 22-9 record in “blowout” games, (margin of victory 5+ runs).


The bottom line here is, if your offense continually fails to deliver in key situations, eventually your bullpen is going to give up runs. Emotionally we will all want to blame the relievers. But the objective evidence points clearly to where the biggest failures have been in these close games.

I don’t have a solution. Some will want to say this is evidence our hitters can’t perform in the clutch. I don’t know that’s true. These numbers are generally not very predictive. They are simply the playing record as it stands to date. Perhaps there is something lacking in the quality of the at bats late in games. To determine that I’d need more granular info than I have. For example pitches per plate appearance in these situations. Or better yet, balls swung at and strikes taken in these situations.

Whatever the reason, and whatever the fix, if the Diamondbacks are to make a run at the Wild Card and into the post season, they are going to need better at-bats late in games and win more of the close games and take the pressure off the pitching staff.