Welcome to the 2026 edition of Ranking the Rockies, where we take a look back at every player to log playing time for the Rockies in 2026. The purpose of this list is to provide a snapshot of the player in context. The “Ranking” is an organizing principle that’s drawn from Baseball Reference’s WAR (rWAR). It’s not something the staff debated. We’ll begin with the player with the lowest rWAR and end up with the player with the highest.
No. 48, Sean Sullivan (-0.4 rWAR)
All things considered, LHP Sean Sullivan (No. 21 PuRP) had an impressive
MLB debut for the Rockies.
After starting the season with Triple-A Albuquerque, the Rockies called up Sullivan on June 12 — the same day they optioned LHP Sammy Peralta and sent Chase Dollander to the 60-day IL.
Colorado’s 2023 second-round draft pick made his first big league start against the A’s in Las Vegas. Even though it was a short outing — as he left early due to an illness — he threw three scoreless innings, holding the A’s to two hits with two strikeouts and one hit by pitch. He tossed 49 pitches, including 33 strikes. The Rockies went on to lose 6-4, but Sullivan made a good first impression.
Unfortunately for 24-year-old Sullivan, the rest of his season didn’t go very well.
He only made five starts, recording an 8.87 ERA, was sent back down to Isotopes twice and spent nearly 10 weeks on the IL with a left shoulder impingement. By the time he was ready for his rehab assignment, it was Sept. 10. He made three starts with the Isotopes, ending his season in Triple-A.
Sullivan went from a 0.00 ERA to 10.29 in his next start to ending his first MLB season with an 8.87 ERA. He went 0-3 in five starts with a 2.01 WHIP, 16 strikeouts, 11 walks, a .343 batting average against and five homers surrendered in 22.1 innings pitched.
In his second start against the Chicago Cubs, Sullivan gave up eight runs on nine hits, including two homers, with two walks and two strikeouts in four innings. He bounced back with a better performance in his next start, only giving up three runs in five hits in five innings. He ended June with an 8.64 ERA and a 0-2 record in four starts.
Considering Sullivan’s struggles, the Rockies sent the former Wake Forest star back down to Albuquerque when Tanner Gordon returned from the 15-day IL on June 30. It didn’t last long as Sullivan was called right back when Tomoyuki Sugano (菅野 智之) was placed on the 15-day IL with back spasms on July 4.
Sullivan made the start for the Rockies on Independence Day against the Giants at Coors Field. San Francisco hit him hard, scoring six runs on 12 hits, including one homer with four strikeouts and two walks in 5.2 innings. The Rockies lost 6-4 and ended up losing Sullivan for what turned out to be the rest of the season.
On the bright side, Sullivan’s final three starts with the Isotopes went well. The sample size was small, consisting of outings of 1.2, 2, and 2.2 innings, but he posted a 2.84 ERA with nine strikeouts, three walks, seven hits and zero homers in six innings. His final outing of the season included four strikeouts.
Sullivan combined to make 14 starts in Alburqueque on the season, finishing with a 5.31 ERA with a 5-3 record. He posted 59 strikeouts in 61 innings with a 1.56 WHIP. The numbers were much higher than his 2.94 ERA in 2025 (with Double-A Hartford, Low-A Fresno and Arizona Rookie League) and his 2.11 ERA (with High-A Spokane and Hartford). But that’s to be expected in the hitter-friendly Pacific Coast League.
Sullivan has never had overpowering velocity. He relies on a low arm slot, command and deception and an arsenal of his four-seamer, sweeper, changeup, cutter and sinker. That being said, he did make the Baseball Americalist of pitching prospects who gained at least 2 mph between 2025 and 2026. He increased his speed from an average fastball of 87 mph last season to 89.8 this season.
Luckily for Sullivan, he has a chance to keep his end-of-2026 momentum going as he’s one of eight Rockies prospects representing the organization in the Arizona Fall League. Known as “finishing school” for young players and a chance to continue to build their skills with coaches and staff, Sullivan and the rest of the Salt River Rafters are playing in games from Oct. 3-Nov. 14.
When Samantha Bradfield wrote Purple Row’s Arizona Fall League preview, she included quotes from Rockies director of player development Chris Forbes, who said he wanted to see Sullivan build up his innings and strength this fall.
“He’s one of those guys that, during the year, just has trouble maintaining weight. He can come in at 205 (pounds), and now he’s pitching at 187 or something at some point,” Forbes said. “So you’re hoping with him that he’s able to get some innings back in and get some feel back, and then ultimately make a better decision on how does he play in next year’s club. Does he come out of the bullpen as a length guy? Is he doing a spot start? I don’t know. But that’s the plan with Sean. I’m just looking at five healthy starts and going into the offseason feeling really good about it.”
Sullivan’s first and only start so far didn’t go very well, however. He took the loss in the Surprise Saguaros 6-4 victory over the Rafters on Oct. 4 when Sullivan gave up seven hits for three runs with no walks and four strikeouts in 2.2 innings.
The season just started, so Sullivan has time to try to reduce his one-start ERA of 10.13. Plus, for Sullivan, it’s not the results that matter as much as the strength training and experience. That’s what will help him start building for a better 2027.
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