The Rockies took a brutal hit to their pitching staff on Friday, as Chase Dollander appeared likely to need surgery on the ulnar collateral ligament in his right elbow. The 24-year-old right-hander was moved to the 60-day injured list, and Colorado responded by calling up lefty Sean Sullivan for his first big league start. In one move, the club lost one of its most effective starters this season and turned the ball over to a far younger arm.
Manager Warren Schaeffer did not sugarcoat the situation, telling reporters, "it's looking like surgery" and noting that a pre-op appointment was "coming up soon," as reported by the Denver Gazette. Dollander had previously said during his rehab that he hoped to avoid going under the knife, but internal evaluations and second opinions have pushed things toward a surgical outcome in recent days.
According to MLB.com, Colorado formally transferred Dollander to the 60-day injured list on Friday and selected left-hander Sean Sullivan from Triple-A Albuquerque to fill his roster spot. The transaction opened a 40-man slot and immediately gave the Rockies a southpaw option to plug into a rotation now missing one of its steadier pieces.
What UCL surgery usually means for pitchers
Ulnar collateral ligament reconstruction, more commonly known as Tommy John surgery, is rarely a quick fix. Most overhead throwers require roughly 12 to 18 months to get back to competitive pitching, according to the Cleveland Clinic. Recovery time can vary based on the specifics of the procedure and the pitcher’s rehab progress, but for many, it effectively wipes out a full season.
Dollander’s 2026 breakout, paused
Before his elbow troubles, Dollander had been one of Colorado’s brighter rotation stories this year. He worked to a 3.89 ERA with 47 strikeouts and 18 walks across 44 innings in 10 appearances, according to his MLB player page. Those numbers marked a clear step forward from his rough rookie campaign in 2025, when he finished 2-12 with a 6.52 ERA over 98 innings. The injury stalls that progress and leaves the Rockies without a starter who was finally beginning to look settled at the major-league level.
Sullivan steps into the rotation
Into that void steps Sean Sullivan, a 23-year-old left-hander and second-round pick from the 2023 draft class. He will make his major-league debut after a steady climb through the minor leagues. Sports Illustrated notes that Sullivan has shown strong control and a solid track record in the upper minors, even if his Triple-A results this season have been uneven. His promotion reflects both his pedigree and Colorado’s urgent need for another rotation option.
The Rockies indicated they will provide further updates after Dollander’s upcoming medical evaluation and any confirmed surgical plan, as reported by the Denver Gazette. For now, the job in front of them is clear: ride a rotation of younger arms, starting with Sullivan, while one of their most promising starters tries to work his way back.
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