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Can the Diamondbacks Pitching Improve ?

Or will an above average offense be wasted ?

2021 Arizona Diamondbacks Photo Day
Joakim Soria returns from IL to Bolster the Bullpen
Photo by Rob Tringali/MLB Photos via Getty Images

The Arizona Diamondbacks have been a somewhat surprising team so far in 2021. After getting off to a poor start, going 5-10, they turned it around by going 10-4 since. They’ve done so primarily on the backs of an offensive surge. Through the first 15 games they scored 4.5 Runs per game, and since then 6.1, thanks to their team OPS improving nearly 150 points! Manager Torey Lovullo has implemented a strategy of platooning and playing in game matchups and substitutions, looking to maximize offense whenever possible. It seems to be working, at least for now.

At the same time the run prevention from pitching and defense only improved marginally during this hot streak from 5.4 to 5.1 R/G. The OPS against improved 60 points, but is still high at .752 (NL Average OPS is .709, and average R/G is 4.37).

It must be noted the rotation has improved since April 17th while the Bullpen numbers have gotten worse. In fact, it’s basically flip flopped. The Rotation got off to a horrible start, and while the bullpen was not “good”, it wasn’t a disaster. Since April 18 the rotation has been pretty good, above average in fact, while the bullpen has been a tire fire.

It’s all added up to a 15-14 record which has them in 4th place in the NL West, 2.5 Games back of the surprising Giants. They’re currently just 1.0 game back of both the Padres and Dodgers for the 2nd Wild Card Spot, and 1.5 games back of the 17-13 Brewers for the first WC.

Nobody knows where the twists and turns of the season will take them from here. As we all know, YCPB. (I miss that site so much). It does seem like the offense should be able to post at least something around league average numbers going forward, even after some regression kicks in. Even before the recent hot streak they were scoring runs somewhere around league average, despite B.A. and OPS that were in the lower 3rd of the NL. They could very well end up being a good deal better than average when it’s all said and done. Especially if Ketel Marte comes back soon and hits the ground running, both literally and figuratively.

As for the pitching staff, while it may feel like significant improvement is unlikely, especially from the bullpen, there are some reasons for optimism.

When I look at the “predictive” stats like xERA from Stat Cast, or FIP/xFIP from Fangraphs I see some glimmer of hope for the rest of the bullpen. We are dealing with very small sample sizes on an individual basis, so all these numbers can be taken with the proverbial grain of salt. But what I did was average the xERA, FIP and xFIP to come up with a composite of predictors, and then compare that to ERA. (Follow the highlighted text if unsure what those acronyms mean) The table below compares that composite to their ERA to give a sense of who might see their run prevention improve, if all other factors remained the same.

Also remember ERA does not take into account inherited runners, and none of these take into account leverage metrics like WPA or Shutdowns/Meltdowns. So consider those caveats as well and follow the links just given for more context.


Positive numbers in the “Difference column” in green mean their underlying peripherals and predictors are better than their ERA, and Red negative means the opposite. Looking at it this way, 7 of the 9 relievers with more than 1 IP should have better ERA than they currently have.

J.B. Bukauskas only has 5 IP, so sample size is TINY. He has only walked one batter, and hasn’t allowed a homer. But the hits he’s given up have been mostly hard contact. Keep pounding the strike zone, and I’m sure the ERA comes down.

Matt Peacock had a really fun debut, but overall in his 9 innings of work, his predictors don’t indicate much positive. 5 is lower than 8 however.

Ginkel is Lopez, Lopez is Ginkel. Well actually Kevin’s underlying predictors are more encouraging than Yoan’s were before he was sent down. 4.24 would be a big improvement. Ginkel has 6 Shutdowns and 4 Meltdowns however. He doesn’t blow up ALL the time. But he blows up too much. I agree with those that feel Ginkel’s high leverage work should be reduced. Options have simply been lacking however.

Stefan Crichton has been pretty good. Certainly better than his ERA indicates. The ERA is a little high due to one bad outing. He’s been the steadiest reliever dating back to 2020. He’s not great, but he’s pretty good, and his ERA should come down.

Taylor Clarke struggles to avoid the long ball. xFIP thinks he’d be pretty good if only a league average amount of the fly balls he allowed left the yard. Until that starts to happen, getting his ERA under 4.50 may be elusive but it’s still good to see he is a candidate for positive regression.

Chris Devenski does not look good to me. I’m not too hopeful here. It’s only 4 IP, so the numbers mean nothing. He is so overly reliant on his changeup and the fastball isn’t very fast at all anymore to keep hitters off the change. I’m not sure what happens here.

Yoan Lopez is right where he needs to be

Alex Young continues a career trend of beating his peripherals. But his peripherals have gotten worse since his rookie season in 2019, so the end result hasn’t been great. I personally think he’s fine as a middle reliever to come in after a righty in mid innings, but he is not well suited to high leverage.

Caleb Smith has been better in the bullpen than he was in his lone start of the year. But I think a mid 4’s ERA is who he really is, pretty much.

So in summary, using the same cast of characters, the bullpen should see their ERA numbers improve as a whole, but they still would not be considered a “good” bullpen. They just shouldn’t be one of the worst.

Joakim Soria shouldn’t even be in the table, but I put him in there just to remind us he’s back. His stuff seemed to have rounded into shape at the end of spring training and maybe the missed month of April will result in him being fresher through the summer. He should help improve the bullpen.


I won’t spill too many more words here. Overall this table may be a case of what you see is what you get. What I wrote up above probably covers it.

Madison Bumgarner’s turnaround is due in large part to improved command and improved stuff. Perhaps the command is better because the stuff is better, providing confidence. Zac Gallen is good, despite struggling in his last outing. Merrill Kelly was improving before going on the IL for “undisclosed reasons”. The last couple of spots have been filled in by Taylor Widener, who is on the IL with a groin strain, and Riley Smith, who’s been fine but maybe a tad lucky.

They’ll probably need rotation re enforcements here shortly if Kelly misses any significant time, but longer term, there is reason to believe the rotation can be somewhat decent going forward. Especially if they can get help from guys like Jon Duplantier and Corbin Martin later in the season. (Dup is on the Taxi Squad for this trip by the way)

Barring outside help, the team may not see tremendous improvement in their run prevention, but it should get somewhat better. As for outside help, let’s revisit that in a month, shall we ? Who knows, if they stay above .500 for the next 4-6 weeks on the strength of a good offense, maybe Mike Hazen will be a buyer come July.