Rockies Prospect Sean Sullivan's Prolonged Success in Double-A Could See Promotion

The Colorado Rockies have had a difficult 2025 season, no doubt, but some of their high-ceiling prospects are finally starting to showcase their talent.

Feb 20, 2025; Scottsdale, AZ, USA; Colorado Rockies pitcher Sean Sullivan (85) as shot during MLB Media Day at Salt River Fields. / Allan Henry-Imagn Images

The Colorado Rockies have had a really difficult stretch of baseball throughout the 2025 season, and their series against the Toronto Blue Jays just emphasized how far away the franchise really is from competing once again.

After being mauled by the American League East division leaders, the Rockies now head into the middle portion of August with a 30-84 record to their name, and practically no momentum to speak of.

Though their farm system is not particularly exceptional either, they certainly have some promising young talent to work with as they head into next year.

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While not officially eliminated from postseason contention, every loss they take pushes them closer and closer to that point. So, focusing on how they can improve the roster on their way to the 2026 season should be a key thing to look into for the coming weeks.

A strong 2025 MLB Draft class certainly helped their outlook, and some of their higher upside prospects beginning to break out have also been a bright spot.

One such player is No. 12 prospect in their system, Sean Sullivan, a starting pitcher who has spent a decent amount of time in Double-A. The great news is that he has rapidly found his footing there and could be on his way to a promotion in the near future if he keeps it up.

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How Has Sullivan Performed Throughout His Time in Double-A Hartford?

Sullivan has spent around one full season in Double-A now, split in half between 2024 and 2025, and in that span, he has dominated the competition as a starter.

In 2024, he made seven starts at the level, posting a 1.97 ERA, 2-0 record, 1.094 WHIP, 24 strikeouts, seven walks, two home runs allowed and 32 total innings pitched.

In 2025, he has seen an even larger sample size there, and in 14 starts has posted a 9-4 record, 2.34 ERA, 0.868 WHIP, 85 strikeouts, 14 walks, five home runs allowed and 6.07 SO/BB.

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It is clear that Sullivan's strikeout pitching has been the key to his success, but also a definitive lack of walks. While he averages around 9.5 strikeouts per nine innings, he is only allowing 1.6 walks per nine innings at this point, which is enormously impressive for any young pitcher.

The hope is that the 22-year-old will be able to continue this production and find himself in Triple-A soon. His pitching has certainly warranted a promotion; it is just a matter of when the franchise feels comfortable that he can handle the next step.

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