This is a pretty good deep dive into how much (or how little) stock should be put into Catcher's ERA... https://tht.fangraphs.com/classic-tht-annual/do-catchers-have-an-era/ Key takeaway is... Looking at catchers who had at least 2,000 matched plate appearances in both odd and even years, I have 70 catchers, and find a correlation of 0.21. This group has an average of 4,343 plate appearance in each year category, which implies that you would have a correlation of 0.50 (where half of the observed difference is skill and half is luck) when you have 16,300 matched plate appearances, about three years of fulltime catching. By comparison, Pina & Grandal have only 1,160 matched plate appearances in a single year, about 1/4 quarter of the sample needed to even get to the 0.21 correlation. If you look at Grandal with the Dodgers, where the samples were larger than we're working with this season, the results were... 2015: Yaz 3.35 | Ellis 3.37 2016: Yaz 3.72 | Ellis 3.28 2017: Yaz 3.22 | Barnes 3.74 2018: Yaz 3.37 | Barnes 3.35 Is Manny Pina a better game caller than Yasmani Grandal? I think that is a very real possibility. Is the 1.27 difference in their Catcher's ERA completely attributable to any edge Pina has as a game caller? I think that is a much less real possibility.