Evaluating the Ray's Starting Pitching Performance Across Catchers

There has been quite a bit of discussion over the last week regarding how to evaluate a catcher's defense, or more specifically his game-calling. Knowing full well that this is a very difficult task, I decided to at least see if there were any trends.  In order to get a read on Dioner Navarro's game-calling, I decided to compare starting pitcher performances when he was behind the plate to that of his backup, Michel Hernandez. At first, I was inclined to look at same pitcher performance across common opponents.  The main weakness would be small sample sizes. How do we know what was game calling vs. the pitcher overruling the catcher or simply not having his stuff on a certain day.

Instead I chose to look at the performance of the rotation as an aggregate with Hernandez vs. Navarro. The biggest obstacle here is an uneven sample size of starts. The ace, James Shields had 8 starts with Hernandez vs. only one for Scott Kazmir. Using the aggregate, largely removes quality of offensive opposition since Hernandez typically catches once per series.  To offset the discrepancy in number of starts per pitcher, I also looked at each pitcher's aggregate  performance with each catcher to confirm any trends.  While there are still sample size issues, there do seem to be some clear trends.

Please click below for the findings:

Wow, that's quite a difference. Again, sample size at play, but it could be indicative of the same trends with less magnitude. The staff averages nearly a full strikeout more per 9 innings with Hernandez than with Navarro. They also average two full walks less with Hernandez. The pitchers are throwing almost 10% fewer balls with Hernandez compared to Navarro.  On the other hand, perhaps as a result of being all over the plate, more balls are leaving the park with Hernandez catching. All in all, the rotation's FIP is .50 lower with Michel Hernandez. Now let's see if we can find our way around the Shields factor.

There are large gaps in the strike % of Price, Niemann, and Kazmir, largely considered the Rays 3 wildest or most inconsistent pitchers. Every pitcher outside of Garza has thrown for at least 65% strikes with Hernandez. On the other hand, there seems to be a trend of more ground balls when Navarro is catching. I am hoping to do some pitch selection analysis between the two catchers.  I included HR/FB to try to capture where the HR numbers may be a bit off. Niemann in particular stands out with only 4.5% HR/FB with Navarro vs. 17.6% with Hernandez. It would seem home runs are the most fluky statistic when dealing with small sample sizes.  Now let's look at each pitcher's FIP components:

Again, every pitcher outside of Garza has fewer walks with Hernandez behind the dish. Every pitcher outside of Sonny has a better K rate with Hernandez. The home run stat is split evenly between the two, once again confirming that to be the most unreliable measure with small sample sizes.

In conclusion, there does seem to be a trend of pitchers having better control with Hernandez calling the game.  It has yet to be determined whether this has to do with pitch selection or location setup.  It does seem to be more than pitchers just not having their stuff, resulting in bad luck for the catcher. On the other hand, pitchers are allowing more home runs with Hernandez.  The larger HR/FB% and even split between the # of pitchers with better/worse HR/9  makes this the most likely aggregate trend to work itself out over time. Overall, pitcher performance has been better with Hernandez to date. The K/BB ratio as an aggregate and individually is pretty startling, in my opinion.  I will try to get to some pitch selection analysis in the future.