Colorado Rockies news and links for Wednesday, February 26, 2025
One of the more intriguing battles in spring training for the Colorado Rockies is the formation of the bullpen. The Rockies ended the 2024 season with an arm barn of hard-throwing, albeit inexperienced, young relievers with a smattering of various experienced players.
The need to address the bullpen has been an issue for the team for thirty years, but it has been even more of a prevalent detriment during its current six straight losing seasons. Since 2019 the bullpen has the highest ERA in baseball at 5.27 with the next closest being Washington’s 4.71 ERA. The team didn’t do much to address the 5.41 ERA from last season; rather, they are relying on a cohesive unit breaking out and hoping that the veteran addition of Scott Alexander would provide a stable backbone alongside Tyler Kinley.
Still, the team brought in plenty of non-roster options to camp should the young arms not perform or indicate a need for some development time. You’ll read more about the status of the bullpen in the upcoming State of the Position series, but one such arm to keep an eye on is veteran right-hander Diego Castillo.
Thomas Harding of MLB.com coined Castillo as a dark horse candidate to make the Opening Day roster:
“But Castillo, 31, who had solid years with the Rays (141 ERA+ 2018-21) and has pitched for the Mariners and the Twins the last two years, could grab a spot if some of the younger hurlers take a step back or simply need more time.”
Originally signed as an international free agent by the Tampa Bay Rays in 2014, Castillo debuted in 2018 at the age of 24 and delivered a strong rookie season. In 43 appearances, he posted a 3.18 ERA in 56 2⁄3 innings with 65 strikeouts and 18 walks. It was a strong first impression in the Rays bullpen and he played a key role in the Rays successful bullpen corp.
From 2018 to 2021 in Tampa Bay, he posted a 2.99 ERA in 183 1⁄3 innings with 218 strikeouts against 65. He was traded to Seattle in 2021 where he pitched to a 2.86 ERA in 22 innings for the Mariners down the stretch. In his lone full season with the Mariners in 2022 he continued that bullpen effectiveness by making 59 appearances and recording a 3.86 ERA but there was a noticeable difference in his performance.
Shoulder inflammation flared up at the end of 2021 and again in 2022 but Castillo spent a minimum of 15 days on the injured list in the latter season. The shoulder may have resulted in the higher walk rate and drop in strikeouts but he was still an effective reliever.
Unfortunately, he struggled immensely in 2023, appearing in just eight games for the Mariners to the tune of a 6.23 ERA, and spending the majority of the year in Triple-A where he had a 5.13 ERA in 43 games.
He latched on with the Minnesota Twins at the end of spring training in 2024 but bounced on and off the roster, appearing in just 10 innings for the Twins at the big league level. In Triple-A last season the struggles remained the same as he made 40 appearances with a 5.59 ERA.
So what has been the issue for Castillo and what can he bring to the table?
Control is the biggest issue behind Castillo’s decline. His walk rate shot up to 14.92% over 84 1⁄3 innings of Triple-A ball over the last two seasons while his 8.9% walk rate from 2018-21 rose to 17.9% in his brief MLB sample size of 18 2⁄3 innings over the last two seasons.
A velocity drop may have also been partially responsible for Castillo’s struggles in 2023 specifically, though his fastball ticked upwards from 93.8 mph in 2023 to 95.9 mph in 2024. Still, velocity doesn’t mean strikeouts as his brief sample size the last two seasons resulted in a 15.5% strikeout rate, a severe drop from the 28.1% he had in the five previous years.
What could work in his favor, and the reason the Rockies are willing to take a flyer on him, is his ability to get ground balls. A career 50.4% groundball rate is certainly attractive for a team that plays half its games at Coors Field.
Castillo features a three-pitch mix that effectively is just two pitches. He mainlines a slider with a league-average horizontal break to the first base side while mixing in a four-seam fastball and sinker that tend to rise to the third base side. With a 33-degree arm slot, Castillo can get some natural cut on his ball to force mis-hits and groundballs. Occasionally he has been known to mix a changeup into his arsenal.
Should Castillo crack the roster, it gives the Rockies another veteran arm looking to bounce back. At 31-years-old he can still turn things around and be a reliable reliever and could be helpful to throw into the mix at various points. His experience is at the backend of games in the last three innings of a game. In 2021 he recorded 16 saves, with 35 total in his career so he can be a closer as needed. Additionally, he has 52 career holds, proving he can be reliable late in games.
If the Rockies want to ease their young relievers into those types of situations, Castillo would be the key substitute to put into that mix to bridge the gap to whoever is serving as the closer.
Despite the last seasons, Castillo still has the potential to be an effective reliever. He’s generally durable with a profile that would work for the Rockies at Coors Field, but he has to reign in his control once again and get back to what he was doing in Tampa Bay. The arm angel has changed only slightly over his career and the pitches have relatively been the same so something has to be figured out was to why the command left him.
There is the wrinkle that someone would have to get the boot from the 40-man roster which can be a tough decision depending on who is and who isn’t performing in camp. Still, if he remains with the team and starts the year in Triple-A Albuquerque, the Rockies have a solid depth piece to supplement should one of the younger players struggle out the gate.
Either way, Castillo is an intriguing arm in camp and will be one of the more notable arms the Rockies could employ in 2025 if things work out that way.
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This week Evan Lang and I celebrate the youth excitement in spring training games while going over projections for Thairo Estrada.
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