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Slinger Saturday: Edwin Díaz

For this new series, I am going to be looking into the top 15 pitchers with the lowest release height. I will work backwards from 15 and post one a week from today until opening day ending with the pitcher who has the lowest release height. I will breakdown their data and what I think makes them so successful (or not) based on the way they throw. Week 1 starts with Edwin Díaz.


Let us begin with the more basic statistics before we jump into the pitch design. 2018 was by far Díaz’s best season, where he led the league with 57 saves in 73 games, threw a career high 73 innings and racked up a career high with 124 Ks (the only time he had over 100 in any season). Díaz also racked up a career low (which in this case is better) ERA- (48), FIP- (39) and FIP (1.61). Coming off the best year of his career, he was then traded to the Mets along with Robinson Cano for Jarred Kelenic and Justin Dunn and had the WORST year of his career.


Díaz’s debut season with the Mets was the start of a rocky year. While juiced balls may play a role in what happened in 2019 to Díaz, it is not the sole cause of his demise. Consistency was something that hurt Díaz as he went from a .61 HR/9 to a 2.33 HR/9 in just one season. Along with the long ball hurting Díaz, he walked many more hitters going from a 2.09 BB/9 to a 3.41. Finally, and what might be the highest jump of first to worst, in 2018 Díaz had a Barrel % of 3.8% which that year was in the top 7% of the league. In 2019, that figure skyrocketed to 10.1% which was bottom 10% in the league.

What went wrong?

When looking at the BaseballSavant statistics, Díaz is one of the best relief pitchers in the game. In his 6 year career so far, he has been in the top 10% of the league every single year in the following categories: xBA, xwOBA, K% and xERA. Looking at his percentile rankings for 2018 vs 2019, a few things stand out to me.

While many things stayed the same, the ones that dropped made very drastic drops. HardHit% went from league average to bottom 2% and Average Exit Velo went from above average to bottom 10%. The biggest drop came from Barrel % which went from elite to terrible in one short year. However, there was one thing that stood out to me when looking at pitch usage.

In 2018, Díaz threw his 4 seam fastball 62% of the time with the slider coming it at 37% usage. While his fastball might have had a better run value than his slider (-14 vs. -5) I would argue that his slider was his better pitch. His slider had a 15% higher Put Away% than his fastball and a 4% lower Hard Hit% than his fastball in 2018. The slider also had a 24% higher K%, 24% higher Whiff% and .060 points of better Average.

In 2019, for some reason, Díaz decided to move away from the slider. The usage dropped from 37% to 33%, the Put Away% and Hard Hit% were almost identical to the fastball, and hitters were batting .297 versus the slider. Along with these changes, the Whiff% also dropped over 10% from the previous year.

What this data tells me is that firstly, with the tremendous year that Díaz had in 2018, the entire league obviously took note of this. While they might not have “figured out” Díaz, they were definitely much better accustomed to his pitching in 2019 than in 2018. Hitters were laying off of the slider more and when they swung, the hitters were usually winning. This lower Whiff% caused Díaz to lean more on the fastball, and hitters took notice of this as well.

At the end of the day, in no way is Edwin Díaz a bad pitcher. In fact, he still may be one of the top relievers in baseball. I think as fans we are unfair in our judgement to him for a number of reasons. The first is that the Mets bullpen ruins a lot of deGrom’s starts to the point where we always say to throw his wins out the window when looking at his greatness. The second is because regression from the season he had in 2018 was bound to happen, but not the way it did in 2019. I hope to see some middle ground of Edwin Díaz these coming years, especially now that he has to try to protect ANOTHER superstar’s leads.

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