Why is Adrian Del Castillo's Projection so Low for the Diamondbacks?

A breakout campaign in 2024 doesn't seem to be registering in his projections. Here is a look into why that is.

Aug 9, 2024; Phoenix, Arizona, USA; Arizona Diamondbacks catcher Adrian Del Castillo (25) celebrates with teammates after hitting a walk off solo home run against the Philadelphia Phillies in the ninth inning at Chase Field. Mandatory Credit: Rick Scuteri-Imagn Images | Rick Scuteri-Imagn Images

As we dive player-by-player into the the Arizona Diamondbacks' player projections, none seems more curious than Adrian Del Castillo's

These projections are derived from the composite average of ZiPS and Steamer, and are prorated to playing time projections created by Arizona Diamondbacks On SI staff.

Adrian Del Castillo, Catcher, Age 25

Adrian Del Castillo 2025 Projection | Jack Sommers

At first blush, the projections seem to be severely underselling Del Castillo, coming in at just a .712 OPS. He burst on the scene red-hot in August, and came through with several big hits and homers, putting his stamp on the season in the midst of Gabriel Moreno's injury.

He later cooled, but the season end line of .313 batting average and .893 OPS was still very valuable. Some of that value was offset by his defense however. He caught just two of 29 base stealers and tallied a total of -3 Defensive Runs Saved. It was the defense that caused him to be optioned back to Reno instead of Jose Herrera when Moreno returned from the injured list.

Why Adrian Del Castillo might outperform his projection

Del Castillo had a true power breakout with AAA Reno, and it was well-supported by the batted ball metrics, for the most part. In 474 plate appearances he mashed to the tune of .312/.399/.603, for a 1.002 OPS.

He took 55 walks and in just 413 at-bats walloped 36 doubles, three triples, and 26 homers. His 144 wRC+ ranked third among 119 Pacific Coast League batters with a minimum of 200 PA.

Diving into his batted ball metrics among PCL hitters. his Average Exit Velocity ranked 9th, Hard-hit rate ranked 5th, and Barrel ranked 4th. In short, there was nothing flukey about his breakout for the Reno Aces.

When he arrived in MLB, he doubled off the wall in Cleveland in his first major league at-bat. In his first game at Chase Field, his first major league home run was a walk-off against the Philadelphia Phillies.

10 days later, in front of his family and friends in Miami against the Marlins, he hit a grand slam and drove in six runs, and followed that with a two-hit game.

Through his first 10 games Del Castillo hit .368 with a 1.092 OPS. three homers and whopping 14 RBI. He showed right out of the gate he could crush the ball, and the power surge in AAA was real.

Why Adrian Del Castillo might underperform his projections

It should be noted that the starting point for these projections is to take the last several seasons, weighting the average of the most recent season more heavily. Then there are adjustments that must be made for the difference between minor league and major leagues.

A heavy dose of regression to the mean is included, especially in cases like Del Castillo's where the player has so few MLB plate appearances.

As great as Del Castillo's was for Reno last year, he struggled mightily in his first run at the PCL in 2023 (73 wRC+), and had a very bad year in 2022, with just a 82 wRC+.

So those seasons still contribute to his overall projection and drag it down a bit. On top of that. he is an older prospect at 25 years old. Age for level is another key factor in evaluating and projecting prospects.

When looking at Del Castillo's game log following that first hot 10-game stretch, we see a drop off to a .728 OPS over his final 15 games. Most importantly perhaps, we need to take note of his 32.2% strikeout rate. That is 45% higher than MLB average.

Were it not for a unsustainably high .438 BABIP (Batting Average on Balls In Play), his high strikeout rate would have caused his batting average and OBP to plummet. For point of reference, league average BABIP was .291 last year. While this number can fluctuate, partly due to luck. and partly due to skill, league leaders are usually between .350-.370.

Finally, nobody on the Diamondbacks had a bigger gap between the expected and actual numbers in 2024. Del Castillo's .384 wOBA was 91 points higher than his .293 xwOBA. League average is .293.

Baseball Savant explains the metric as follows:

Expected Outcome stats help to remove defense and ballpark from the equation to express the skill shown at the moment of batted ball contact. By looking at the exit velocity and launch angle of each batted ball, a Hit Probability is assigned based on the outcomes of comparable historic balls in play.

By accumulating the expected outcomes of each batted ball with actual strikeouts, walks and hit by pitches, Expected Batting Average (xBA), Expected Slugging (xSLG), and (most importantly)Expected Weighted On-Base Average (xwOBA) tell the story of a player's season based on quality of and amount of contact, not outcomes.

Summary

The second part of this article may feel like it's beating up on Del Castillo, but it's not. When one sees such a large discrepancy in the results from 2024 and the projection, it deserves a thorough explanation, which is what is provided here.

At the end of the day, Del Castillo has just 87 MLB plate appearances. His numbers were already regressing to the mean, but he was sent back to Reno before they could fall further, leaving them frozen in time and creating a certain impression.

Finally, in order for Del Castillo to earn more playing time, General Manager Mike Hazen made it very clear that he has a lot of work to do on defense. At the moment he is still behind Jose Herrera on the depth chart for the backup catcher role. Furthermore, Hazen said the team has no plans to utilize him as the DH. Thus, his playing time projection is a modest 178 PA.

It's my personal belief that if Del Castillo is able to improve his defense and earn the confidence of management, he'll get closer to 250 PA, and should be able to post better numbers than this projection. I would take the over, but caution against unrealistic expectations based on 87 MLB PA in 2024.

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