Mariners 2022 Report Cards: Grading the season for Diego Castillo

Diego Castillo is a prime example of why you need to look deeper at the numbers for relief pitchers. You might see his ERA this year and think “hmmm, 3.64. Yeah, that’s not too bad, but it’s not anything special.” Most of the time, you would be right on someone with an ERA in that range. For Castillo, you would be sorely mistaken.

In his first full season with the Mariners, Castillo made 59 appearances. He would total 54.1 IP and earn seven saves for the Mariners, serving as one of their secondary closers. His K/9 was down a bit, and the BB/9 was up. He’s younger than people realize, has a lot left in the tank, and the 29-year-old was just doing what worked this year on the mound.

I’m giving Diego Castillo a B+ on his 2022 grade for the Mariners

Here’s why. If you look at the period from May 3rd to May 20th, Castillo was awful. He had six appearances, only 3.1 IP, and gave up 11 runs. It’s awful, and there isn’t much good that you can take from it. That’s an ERA of 29.70. Woof.

What about the rest of the season though? I think you should be able to tell where it is that I am going with this. In his other 53 appearances and 51 IP, Castillo had an ERA of just 1.94. That’s pretty incredible if you ask me. If he did that all season, you would be looking at an easy A grade. Because of that rough blip, he gets downgraded to a B+.

You could further the up-and-down case by focusing on the four-game stretch in early September where he gave up five runs. What it really does is show how often Castillo came in and shut down the opposing team. From May 23rd to August 27th. Diego Castillo threw in 31 games, with 30.2 innings, and had a minuscule ERA of just 0.88. Shoot, his slash line over that time was .120/.221/.190. He was nigh untouchable for four months.

The underlying statistics further prove how good he was. 90th percentile in average exit velo, 95th in hard hit, 88th in xBA, and 86th in xSLG. He continued with his normal career path of almost all slider/sinker, with 63% slider, 31% sinker, and just 6% fastball. Players chased a career-low against him, but they still couldn’t hit when he put it in the zone.

Also, for those worried about his velocity, it ticked back up a bit after being down in 2021. The slider is back to his career average, with the sinker and 4-seamer being a bit lower.

Diego Castillo has turned out to be a pretty good addition to the Mariners ever since acquiring him from the Rays at the 2021 deadline. He earned a B+ for 2022, and I’m excited to see him come back in 2023 as a part of a very strong Mariners bullpen.