The Roller Coaster Ride Called Luis Castillo

After posting a 3.12 ERA over 15 starts last season in his MLB debut, which by the way was fully supported by exciting skills, Luis Castillo was rightfully a favorite target for many fantasy owners heading into the year. Unfortunately, his follow-up has been a big disappointment. The 25-year-old has posted a 4.66 ERA, while both his strikeout and ground ball rates have tumbled. He has also been unable to curb his severe gopheritis. When we talk about pitcher inconsistency, Castillo has been the epitome. If we were to ride on a baseball themed roller coaster, it would most certainly be named after him.

Want to go for a ride?

Looks like fun! Look at all those nerve-wracking hill climbs, followed by thrilling drops!

Here’s the same data, now in tabular form:

Up and down and up and down and up and down. Wheeeeeeeeeeeeeeeeeeeee. But has he really pitched all that differently throughout the year? You be the judge. We’re going to add a host of additional metrics along with ERA.

Let’s start from left to right. Except for this month, his strikeout rate has been down all year. On the season, his fastball velocity is down 1.4 miles per hour, which is significant, but not seriously concerning given his baseline (97.5 mph) was so high to begin with. He has thrown his four-seamer less frequently in favor of his sinker and also upped his changeup usage. Though the sinker’s SwStk% is above last season’s mark, it’s still by far his worst whiff generating offering. So obviously more sinkers would result in fewer strikeouts. Interestingly, his ground ball rate has declined, even despite the increase in sinker usage.

His changeup is an elite pitch and his best, so it makes sense for him to throw it more often. That he has thrown it even more and also upped his SwStk% is an impressive feat. Overall, his SwStk% is actually up meaningfully from last year to an elite level. So how has his strikeout rate declined? Plugging in his strike type rates into my xK% equation actually suggests he’s been a bit unlucky. He has lost a significant rate of foul strikes, but the strikeout rate drop should have been less severe. On a monthly basis, his strikeout rate hasn’t jumped around enough to drive such ERA fluctuations.

Castillo’s control has improved markedly in the last three months, but again, there’s little correlation with ERA. He is throwing a higher rate of strikes this year, and his walk rates at High-A in 2016 and Double-A in 2017 support excellent marks.

Now we move on to the trio of luck metrics. Aside from an inflated April mark, his BABIPs until September have remained relatively stable. You don’t typically see a .282 BABIP associated with a 6.75 ERA! On the HR/FB rate front, he has fluctuated around the 20% mark in four months, with opposite extremes in July and September. Only July does his HR/FB rate make sense pair with his ERA.

Now that brings us to LOB%, which, finally, provides an explanation. A picture is worth a thousand words…

The LOB% is low, the ERA is high, the LOB% is high, the ERA is low. That’s exactly how it should work.

Last, we move along to the end to find that his xFIP hasn’t varied anywhere close to the degree that his ERA has. After diving into his monthly splits, we now know that it has primarily come down to his LOB% bouncing all over the place, which is a metric a starting pitcher doesn’t have a whole lot of control over. A sustained high HR/FB rate (except for July) could also be blamed for the overall disappointing year, but isn’t really the explanation for the monthly roller coaster ride.

So yeah, it wouldn’t surprise me if several Castillo owners who held all year have pulled all their hair out. It must have been super frustrating. But man is this an intriguing skill set. He’s got the velocity, the devastating secondary pitch and sharpened control. Depending on how he finishes the year, he’ll likely go cheaper in next year’s drafts. With a reasonable price this time around (he was wayyyyyyyy too expensive this year given the risk), I’m totally a buyer.