The impact of Reds catchers on pitching success

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When you think about a catcher’s defense, chances are the first two things that come to mind are blocking and throwing. Perhaps you’ll also think about framing, though framing still generates a mixed reaction from fans. However, a catcher’s defensive aptitude goes well beyond these three factors. Game calling and building a strong relationship with your pitching staff are under-appreciated skills, but incredibly important ones. Perhaps the reason why they are under-appreciated is that there is no good way to quantify those skills. If you dive into the data though, it’s possible to find a way to quantify those skills a bit. To do this, we will look at three seasons of Reds data, spanning from 2018 through 2020.

Curt Casali joined the Reds in 2018, remaining with the team for three seasons. In that time, he started 114 games behind the plate and appeared in a total of 134 games behind the plate. He caught a total of 1014 innings. During the same timeframe, Tucker Barnhart played in 256 games, catching 2036 1/3 innings.

When Casali joined the team, Barnhart was the reigning NL Gold Glove winner, primarily on the strength of his blocking and throwing skills. In his first Gold Glove season, Barnhart graded out as a very poor framer, accruing -10 “runs extra strikes” per Statcast. Meanwhile, prior to joining the Reds, Casali ranked as average or better in framing in both 2015 and 2016. He only played nine Major League games in 2017.

After joining the Reds, Casali continued to grade out around league average in framing. Barnhart continued to struggle with framing in 2018, ranking as one of the worst framers in the game at -18 “runs extra strikes” by Statcast. However, his framing improved significantly in 2019 and 2020, ranking a bit better than league average.

As previously mentioned, blocking, throwing, and framing are all just a part of the story. To attempt to quantify other skills such as game calling and catcher-pitcher relationships, we will first look at how the pitching staff performed as a whole when Casali or Barnhart was behind the plate.

Most notably, Reds pitchers had a higher strikeout rate and lower walk rate with Casali catching. Their ERA was also significantly lower with Casali, though it’s important to note that a multitude of other factors contributes to ERA that is outside of the pitcher and catcher’s control. Still, over those relatively large sample sizes, it’s notable that there’s that large of a difference.

On an individual season level, we can actually get more information. While FIP (fielding independent pitching) splits by catcher aren’t available on any website, we can calculate this for individual seasons using this formula from Fangraphs.

Similar to the overall stats, we can see that in each individual season, pitchers again had a lower ERA and higher strikeout rate with Casali. In 2018 and 2020, pitchers again had a lower walk rate with Casali by a significant margin, though they actually had a slightly higher walk rate with Casali in 2019. Pitchers had a lower FIP with Casali than with Barnhart. It’s also important to note the close correlation between FIP and ERA in each of these seasons.

Another interesting observation here is regarding Barnhart’s strikeout and walk rates in 2018 and 2019. While there was a notable increase in strikeout rate from 2018 to 2019, you can see that the walk rate was nearly identical in both seasons. The pitching staff as a whole saw a rise in strikeout rate from 20.0% in 2018 to 25.6% in 2019, while their walk rate rose a bit from 8.5% in 2018 to 8.8% in 2019. We know that Barnhart significantly improved in framing from 2018 to 2019, but can also see that the extra strikeouts did not come from walking less batters. Therefore, we can infer that the increase in strikeout rate was likely due to a talent change in the pitching staff as a whole, rather than something the catcher could control. We can also notice the same type of uptick in strikeout rate when Casali was behind the plate, further solidifying the argument that it was an improvement on the pitcher level.

It’s also interesting to note that, while Casali is now with the San Francisco Giants, pitchers have continued to have success with him behind the plate. Through Saturday, Giants pitchers have a 1.59 ERA along with a 23.8% strikeout rate and 6.9% walk rate with Casali. By contrast, Giants pitchers have a 3.88 ERA, 24.5% strikeout rate, and 9.5% walk rate with Buster Posey behind the plate. Casali also caught five straight shutouts with the Giants this year. The San Francisco Chronicle recently wrote about how Casali was helping Giants pitchers flourish this year, though the article is behind a paywall.

With Individual Pitchers

We can also look on an individual pitcher level to see how these pitchers fared with each catcher. Over the course of those three seasons, four Reds pitchers threw at least 90 innings with each catcher: Luis Castillo, Anthony DeSclafani, Tyler Mahle, and Sonny Gray. Let’s take a look at those four and see how they performed with each catcher.

Luis Castillo

Luis Castillo continues to show a very similar trend to the one we noticed in the overall statistics. His ERA and FIP was significantly lower with Casali, being even more pronounced in 2018 and 2020. His strikeout rate was also significantly higher with Casali in 2018 and 2019, though it was actually a bit better with Barnhart in 2020. His walk rate was much better with Casali in 2018 and 2020, though was quite a bit better with Barnhart in 2019.

Essentially, as a whole, Castillo appears to have been a completely different pitcher depending on who is behind the plate. So far in 2021, Castillo has made four starts with Barnhart, posting an ugly 8.83 ERA, along with a 16.3% strikeout rate that is nowhere near his career normal. Opponents have also posted a 1.034 OPS against Castillo in those four starts. The positive sign in those four starts has been a 7% walk rate that is significantly better than his career average.

Tyler Stephenson has caught Castillo’s other two starts, with Castillo posting a 2.19 ERA along with a 20.8% strikeout rate and minuscule 4.2% walk rate. Still, we would want to see a much larger sample size this season to draw any real conclusions. It will be interesting to monitor these catching splits with Castillo as the season progresses to see if the trend continues.

Anthony DeSclafani

DeSclafani showed much of the same trend, having more success with Casali behind the plate for the most part. His ERA was better with Casali in all three seasons, and his FIP was also better with Casali in 2019 and 2020. In 2018, however, he had a better FIP with Barnhart, due in part to a lower walk rate but also due in part to home runs allowed. In 2018, he allowed 13 home runs with Barnhart and 11 with Casali, in fewer innings.

While there was a notable difference in strikeout rate with the two catchers in 2018, the difference was negligible in both 2019 and 2020. We notice a bit of the opposite with walk rate, as it was worse with Casali in 2018 but significantly better with Casali in 2019 and 2020.

It’s important to caution that DeSclafani only threw 33 2/3 innings in 2020, significantly less than the other starters highlighted in this section, so small sample size could absolutely be a factor here. It’s difficult to read into those 2020 numbers here given that one particularly good or bad start can easily skew the numbers in this small of a sample.

DeSclafani and Casali have reunited in San Francisco this season, though Casali has only caught one of DeSclafani’s six starts. It will be interesting to monitor how the two work together this season, particularly compared to how DeSclafani pitches with Buster Posey behind the plate.

Tyler Mahle

Mahle really only has two seasons’ worth of data to compare, as Casali only caught one of his starts in 2020. In 2018, we can see that Mahle had a much lower ERA, FIP, and walk rate with Casali, and very similar strikeout rates between the two catchers. A large part of the FIP difference can be explained by home runs, as he allowed 16 with Barnhart behind the plate compared to just one with Casali.

In 2019, Mahle posted a slightly lower ERA with Barnhart, though FIP and strikeout rate favored Casali. There was nearly no difference in walk rate between the two. Given that his rate of allowing HR was actually slightly higher with Casali, the difference in FIP can be explained by the drastic difference in strikeout rate. As a whole, Mahle showed an increase in strikeout rate from 2018 to 2019, rising from 21.7% to 23.2%. However, as we can see, the strikeout rate actually dropped with Barnhart, and all the gains came with Casali behind the plate.

The one thing we can take from the 2020 data is that Mahle improved significantly with Barnhart behind the plate. Perhaps this was due at least in part to a change in game calling by Barnhart or an improvement in their relationship, but it’s far more likely that Mahle just improved as a whole from 2019 to 2020.

Sonny Gray

When you think about who you’d expect to benefit most from having Casali behind the plate, the first name that likely comes to mind is Sonny Gray. Given that Gray and Casali worked together at Vanderbilt in college, they already had an established relationship prior to pairing with the Reds.

This appeared to pay some dividends in 2019, as Gray’s ERA, FIP, strikeout rate, and walk rate were all better with Casali behind the plate. However, this didn’t really hold true in 2020. On the contrary, Gray was actually significantly better with Barnhart behind the plate, pitching like an ace with Barnhart.

A quick look at the game log shows that Casali was behind the plate for Gray’s September 1 start against the Cardinals in which Gray went 2/3 of an inning, allowing six runs on five hits, with three walks and a strikeout. If you remove that start, his FIP with Casali drops to 3.33 and his ERA drops to 1.69, indicating that the one poor start skewed the stats fairly significantly. This shows why you must be careful trying to analyze this type of data if the sample size is not large enough, as it can be easily skewed.

Conclusions

So what conclusions can we draw with this data? The argument that Castillo struggles with Barnhart behind the plate certainly seems to hold some water. On an individual pitcher level, it seems that some pitchers will perform better with particular catchers. We can also conclude that it’s tough to determine this unless you have a large enough sample size, ideally spanning multiple seasons.

On the level of the pitching staff as a whole, it’s tough to determine whether the difference is truly the catcher, or a differing quality of pitchers being caught by that catcher. Once again, you’ll want multiple seasons’ worth of data to be able to draw accurate conclusions. In the end, it seems that there is something there, but it’s still difficult to determine just how much of it is real.

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