A Deep Look at D-backs Catcher's ERA is Quite Illuminating

A study into the catcher's ERA with Diamondbacks pitching staff and how Gabriel Moreno and company have done

Sep 16, 2024; Denver, Colorado, USA; Arizona Diamondbacks catcher Gabriel Moreno (14) during the fifth inning against the Colorado Rockies at Coors Field. Mandatory Credit: Ron Chenoy-Imagn Images / Ron Chenoy-Imagn Images

The Arizona Diamondbacks have gone through four catchers this season with three of them getting extended runs with the pitching staff. Gabriel Moreno, Adrian Del Castillo, and Jose Herrera have each worked with the pitchers the most. Tucker Barnhart played sparingly.

All four of them have had big moments, but there's been a large discrepancy between their individual catcher ERAs and their ERA with specific pitchers, especially the bullpen.

What is Catcher ERA?

Quite simply, it's the ERA that a catcher has when he is catching the game. This is intended to be used similar to pitcher ERA only it's for all nine innings of the game regardless of the pitcher whereas pitcher ERA is tied to each specific pitcher.

Additionally, we can look at the ERA that a pitcher has with a specific catcher such as Justin Martinez's ERA when pitching to Gabriel Moreno.

Both of these numbers are important when it comes to judging how well a pitcher AND a catcher are working together and whether there could potentially be any battery issues that are arising.

While it isn't the sole way to judge a catcher's performance behind the plate in terms of framing and pitch calling, it is another, yet important piece of the puzzle.

Moreno's overall catcher ERA has been the team's lowest by a large margin at 4.39. Jose Herrera, with nearly a third of Moreno's plate appearance, has the third-lowest ERA at 4.76. That's a drop-off of 47 points.

Del Castillo had the worst ERA with a 5.46. A mitigating factor in his case might be that he arrived when just multiple pitchers were returning from injury and re-finding their stuff. A lot of the bullpen began to struggle around that time too. Tucker Barnhart had a 4.61 ERA, second lowest but also played not many games until he was cut.

Which Pitchers Appear to Be Working Best with Which Catcher?

The age-old idea that pitchers work better with a singular catcher versus anyone else is likely true. There have been many instances of pitchers having a "designated catcher", such as Zack Greinke with Jeff Mathis.

That isn't possible for the bullpen however. Therefore when a large portion of the bullpen works far better with a singular catcher versus another, it does tend to raise questions as to why and what is causing that. Is it pitch calling? Is it framing?

This is especially true when you see a sudden bullpen collapse coincide with a changing of the guard at catcher such as when Gabriel Moreno went down with injury or even on Sunday against the Brewers when after Moreno left, Milwaukee came back from eight runs down to win.

Let's start with the starting rotation. Stats are through games of September 24, 2024.

It's well-known that Zac Gallen does better when Jose Herrera is catching him versus Moreno or any other catcher. The ERA backs that up as over 54.1 innings, he has a 2.82 ERA. In 70.2 innings with Moreno, he has nearly double the ERA at 4.35.

Brandon Pfaadt performs nearly even with both Herrera and Moreno, however, the split in innings is large. In 93.1 innings with Moreno, Pfaadt has a 4.63 ERA versus a 4.45 ERA in 32.1 innings with Herrera. With Del Castillo in 14.1 innings, it's 10.05.

Ryne Nelson has broken out this year and the majority of that breakout has come with Moreno behind the dish. In 62.1 innings, he has a strong 3.47 ERA. With Herrera, over 18.1 innings, it's a 4.91 ERA. However, with Del Castillo it's a strong 3.48 ERA in 31 innings.

Jordan Montgomery has struggled with all three catchers, but has done best with Moreno. Over 54 innings, he has a 5.17 ERA. Over 20.1 innings with Del Castillo, it's 7.08. With 18.2 innings and Herrera, it's 6.75.

Merrill Kelly hasn't pitched much but he's been dominant with Moreno to the tune of 1.90 over 23.2 innings. He had five scoreless with Herrera and a 5.85 ERA over 32.1 innings with Del Castillo.

Eduardo Rodriguez has the same story with 6.1 brilliant innings with Moreno and a 2.84 ERA versus a 5.62 ERA with Herrera over 24 innings and a 6.60 ERA with Del Castillo over 15 innings.

Yilber Diaz has been far better with Herrera with a 0.71 ERA over 12.1 innings against an 6.94
ERA over 11.2 innings with Moreno. In four innings with Del Castillo, he has a 4.50 ERA.

Former closer Paul Sewald has struggled this year but excelled with Moreno. Over 16,1 innings, he had a 3.31 ERA. Over 11 innings with Herrera, it's a 6.55 and with Del Castillo and 5.1 innings, it's 6.75.

Justin Martinez had a disastrous outing on Sunday that has followed his track record this year when pitching to Herrera. Over 14.1 innings, he has a 6.91 ERA. Over 37.2 innings with Moreno, it's a sparkling 1.43 and with Del Castillo and his 10.2 innings, it's 2.53.

Kevin Ginkel has pitched 36.2 innings with Moreno and has a 3.68 ERA while with 14.1 innings with Herrera, he has a 4.40 ERA despite a far lower OPS against with Herrera. With Del Castillo over 10.1 innings, he had a superb 0.87 ERA.

Ryan Thompson has struggled of late, but over 33.1 innings with Moreno, he has a 1.35 ERA and .512 OPS against. With Herrera over 12 innings, it's a 6.75 ERA and over 300 points higher OPS. With Del Castillo over nine innings, it's an unsightly 9.00.

Left-hander Joe Mantiply has pitched 29.1 innings with Moreno and recorded a 4.30 ERA and .664 OPS. Over 12.2 innings with Herrera, it's 7.11 and over a 100 points higher OPS. He's throw six scoreless innings with Del Castillo.

A.J. Puk has pitched brilliant with all three relievers, making them all look like Johnny Bench. With Del Castillo, he had 10.2 scoreless innings. With Herrera, he had 9.1 scoreless innings. With Moreno, over six innings, he had a 1.50 ERA.

Bryce Jarvis pitched a lot this year before getting injured and recorded a 2.79 ERA with Herrera over 9.2 innings. In 37.1 innings with Moreno, he had a 4.10 ERA.

Moreno's overall catcher ERA being just 37 points different from Herrera's doesn't seem drastic, however, if you remove Zac Gallen from the equation, that ERA difference rises quite a bit. It makes for a larger split between the two well-regarded catchers.

Moreno without Gallen's innings drops his ERA to 4.30 from 4.35. However, Herrera without Gallen's innings, ERA rises from 4.76 to 5.21, nearly as much as Del Castillo's.

Plus, there is a stat on Baseball Reference that measures how a player does at calling pitches for a game. The definition of it is the number of runs above or below average the catcher was for the pitcher ERA.

Gabriel Moreno is at +4, a quality number that has helped D-backs pitches obtain a potentially lower ERA. Jose Herrera and Adrian Del Castillo are both at -1.

That means that according to this stat, they have been a liability at calling pitches and/or are potentially costing the team a run. In total, this shapes to about a game or so in wins between Moreno and the other two.

This includes the fact that Moreno has caught nearly twice or more what the other two catchers have caught.

Another indicating statistic for these catchers is Defensive Runs Saved Above Average or DRS. Moreno is among the best in the league with +10. Herrera is -2. Del Castillo is -2 as well.

While evaluating catcher defense is an inexact science and it's hard to comprehend all that they do and put that into numbers and data, this data does seem to potentially indicate that the Arizona Diamondbacks have a significant backup catcher problem.

Additionally, it could significantly cost them games or impact the team's overall pitching and ERA, especially the bullpen. It might've led to some of the team's recent pitching woes that have been written about and studied extensively.

Still, the Diamondbacks haven't pitched as well as they needed to in order to lock up a playoff spot. That onus falls on the whole team and not just any catchers.