A detailed view of a Colorado Rockies hat and glove on the bench against the Atlanta Braves in the ninth inning at Truist Park. Brett Davis-Imagn Images

Rockies Rising Star Sean Sullivan Potential MLB Rotation Candidate in 2026

Originally posted on Colorado Rockies on SI
By Matt Postins | Last updated Oct 11, 2025 9:00 PM ET

The Colorado Rockies weren’t shy about calling up McCade Brown in August, even though he had never thrown a single inning above Double-A.

Could Colorado give Sean Sullivan the same treatment? He’s certainly pitching like he should get a chance.

Recently, MLB Pipeline handed out their top prospect awards for each team. Outfielder Jared Thomas, the Rockies’ No. 8 prospect, was named the top position player. Sullivan, a left-handed pitcher who is the organization’s No. 12 prospect, was named the top pitcher.

Sean Sullivan in 2025

Isaiah J. Downing-Imagn Images

The season got off to a slow start for Sullivan, who needed time to recover from a hip issue. He did a rehab start in the Arizona Complex League and at Class-A Fresno before he went to Double-A Hartford and basically picked up where he left off in 2024.

In 18 starts for the Yard Goats, he went 9-6 with a 3.14 ERA. He struck out 95 and walked 24 in 97.1 innings. Batters hit .227 against him and he had a 1.09 WHIP. High strikeout and low walk ratios have marked his time in the system. Combined with his rehab work, he had a 2.94 ERA, which was best in the organization for pitchers with 100 or more innings. His 4.16 K/BB rate was also best in the Rockies minor league system.

Colorado thought enough of Sullivan to take him in the second round of the 2023 MLB draft out of Wake Forest and sign him to a $1.7 million bonus. He put himself on the map with scouts in 2022 as he went 5-3 for the Demon Deacons, with a 2.17 ERA an all-ACC selection.

The Rockies dropped him into their system and gave him three games and four innings to give them a taste of what he could do against professional hitting. He went 1-0 with no ERA, with 10 strikeouts and one walk in four innings. It was not a tease. It was a sign of things to come.

In 2024 he began the season with High-A Spokane and was eventually promoted to Double-A Hartford. He was exceptional at both affiliates. With Spokane he was 7-2 with a 2.16 ERA in 14 starts, with 101 strikeouts and eight walks in 83.1 innings. With Hartford he went 2-0 with a 1.97 ERA in seven starts, with 24 strikeouts and seven walks in 32 innings. Combined, he was 9-2 with a 2.11 ERA in 21 starts, with 125 strikeouts and 15 walks in 115.1 innings. Batters hit .212 against him and he had 0.91 WHIP.

Sullivan isn’t with the Rockies prospects who are playing in the Arizona Fall League, which started on Monday. Games for Saturday and Sunday were postponed and canceled, in the case of Sunday’s games, due to Hurricane Priscillia. Rockies prospects, who are playing with the Salt River Rafters, will be in action again on Tuesday when they host Glendale.

This article first appeared on Colorado Rockies on SI and was syndicated with permission.

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