The Mile-High Four Seamer: Dugan Darnell’s Rise to The Show

Dugan Darnell's high-vert fastball is being hampered by altitude

Dugan Darnell isn’t a top-30 prospect with the Rockies, fans probably haven’t heard of him, and he wasn’t even drafted. He’s had a good, not great, minor league career and is approaching 27 years of age. Why then is he worth mentioning? To put it simply, he has a big-league fastball and the Rockies might not even know it.

One of the downsides of being in Denver is that pitches don’t move the same way at Coors Field as they do at sea level. With less dense air molecules at altitude, the ball exerts less force on the air around it, leading to less seam and spin-induced movement. Elevation can take up to 1″ of vertical movement off of a fastball per 1,000 feet–so attributing any movement differences from 2022 to 2023 (Hartford, CT vs. Albuquerque, NM) is a reasonable assumption. This isn’t new information, however, in the day of the elevated four seam fastball, movement–and evaluation of movement–are becoming more and more valuable to teams. It’s easy to scout players remotely now with access to video and data sharing amongst teams and even if the Rockies don’t see the unique value of Darnell’s fastball, other teams certainly will.

In regard to the nitty gritty of Darnell’s pitch shapes, his fastball is clearly his best pitch. In his three-year minor league career (2021-2023), he has averaged 93 mph on the dot. He touched 97 in 2023 and averaged 18″ of induced vertical break (IVB) with 10″ of horizontal break (HB) at a 6′ release height with just shy of 7′ of extension. While none of those metrics really stand out, it’s crucial to mention that he had that movement profile on his heater while playing half the season in Albuquerque, New Mexico. Albuquerque is also a mile-high city and has a similar effect on pitch movement. While in Hartford during the first half, he averaged 2-3″ more vertical movement on his fastball, just like he did in 2021 and 2022. In those first two seasons with the Rockies’ minor league affiliates, he averaged over 20″ of induced vertical break (IVB) on his heater, which would’ve been at the top of all MLB fastballs.

In combination with his lengthy extension to the plate and nearly MLB average velocity, the movement in Albuquerque on Darnell’s fastball makes it a plus MLB pitch. The movement on his pitch will only get better if he were to switch organizations and get back to sea level. Additionally, the dry environments of the PCL likely worsened his grip on the fastball, both in terms of tackiness on his fingers and his ability to narrowly grip the fastball. These effects also likely explain the pitch’s loss in spin rate from 2,400+ rpm to around 2,300 in 2023. In essence, his fastball is better at normal altitudes and any differences from past seasons in movements could also be attributed to atmospheric factors.

A team such as the Dodgers or Rays could be smart to add Darnell as part of a trade package knowing that his movement would improve with a scenery change and that a more strategic location on the fastball would also lead to more swings and misses. While the Rockies pitchers sometimes need to shy away from throwing their four seamers up in the zone due to diminished movement, in other ballparks, a fastball like Darnell’s should, more often than not, be thrown to the top third of the zone. Location is another important piece to the Darnell puzzle because he actually throws his fastball down in the zone, particularly relative to league-wide four seam fastball location.

To pinpoint the difference in potential strikeouts due to vertical location differences, we need to take a trip down memory lane. Before Darnell was signed by the Rockies heading into the 2021 season, he played two seasons of independent baseball following a successful four-year stint as a hitter at Division III Adrian College in Michigan. In his second year of Indy Ball, Darnell played in the USPBL, heavily scouted by the Twins, producing the flash-in-the-pan playoff starter Randy Dobnak. Darnell’s 2020 season was so absurdly good that the Rockies came calling post-pandemic roster cuts. In 28.2 innings, he allowed just one earned run with a whopping 52 strikeouts. That success led to an amazing start with the Rockies: he made quick work of Low-A Fresno, allowing one earned run in 13.2 innings with 17 strikeouts and zero walks. He finished the season with another successful stint in High-A Spokane, tossing 41 innings with 63 K’s and a 2.66 ERA. He ended the season as a Rockies MiLB postseason All-Star.

Between 2021 and 2022, however, something changed. He stopped throwing his fastball up in the zone. This led to a massive drop off in chase rate on the pitch. While he still struck hitters out–hitters still had a hard time putting the bat on the ball–they don’t chase four seam fastballs down out of the zone the same way they chase four seams up. One version is a ball the whole time (ball-to-ball) and the other version is a strike out of the hand before leaving the zone due to the vertical movement (strike-to-ball). His chase rate went from among the highest in minor league baseball (nearly 40% on the fastball) to half that (around 20%) without any change in velocity or movement. This location strategy had such a drastic change, in fact, that his walk rate rose from 1.6 walks per nine in 2021 to 6.2 walks per nine in 2022 despite a higher in-zone rate with the fastball in 2022. Yes, you read that correctly, he threw his fastball in the strike zone more in 2022 than in 2021, yet his walk rate rose by 4.5 walks per nine innings.

Now, there’s no reason for Darnell, the Rockies, or any other suitor of his services to cry over spilled milk. The important part here is how easy it would be for him to get back to what he’s already shown he’s capable of. Take Darnell out of the mountains and tell him to throw up in the zone and, all of a sudden, he’s back to being elite. This line of reasoning doesn’t even consider the fact that he’s added a nasty splitter in the last two seasons and has been working on a harder slider to complement his big curveball. His splitter, thrown as his primary off-speed pitch at around 35% usage, averages 7″ of IVB with 12″ of HB at 85 mph. The 11+” of vertical movement separation from the fastball is significant enough to make it a plus MLB pitch in a vacuum. Also considering Darnell’s high release height, the pitch becomes even better. The splitter actually had a higher miss rate than his fastball in 2023, showing both the success of its development and how location has diminished the heater’s value.

His slider and curveball are his third and fourth pitches, respectively, but the slider has the makings of an average MLB pitch. He throws the gyro slider in the mid-80s with 4″ of IVB and two inches of glove side movement (-2″ HB). Again, his high release height makes the slider descend at a steeper angle than most with that shape, leading to more misses than the movement profile would suggest, similar to the slider shape (but 4 mph slower) that led to a 3-year, $33 million contract for Robert Stephenson this offseason. His curveball falls in the ‘get me over’ category at 76 mph with -15″ of downwards movement from topspin. It’s really only useful for getting hitters out in front and generating taken strikes, however, if thrown infrequently enough, it has the power to win any at bat so long as the hitter doesn’t expect it.

Darnell has a balanced four-pitch mix that is platoon-neutral. The splitter is better to lefties and the slider is better to righties, however, his three best pitches can be thrown to any hitter in any count. With improved command in 2023 (walk rate down to 3.8 walks per nine), increased in-zone rates, and still bad location strategy, Darnell definitely has the tools to be an above-average MLB reliever. Execution is paramount for any pitcher but especially for one with a primary pitch that screams to be thrown in a particular part of the zone. Maybe it’s the Rockies’ fault, maybe it’s accidental, but regardless, it is a small adjustment that can lead to massive gains. Despite decreased movement in Colorado and Albuquerque, Darnell still has enough movement to stifle bats at his home stadiums as his movement will be the best relative to the other pitchers. A fastball can be enough to make a living, but his other pitches are worthy supporting characters. Whether he makes it to the Big Leagues with the Rockies or another team, Darnell is good enough to keep an eye on heading forward.

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