Sullivan all the wiser after 'wake-up call' of a debut season

SCOTTSDALE, Ariz. -- Rockies left-handed pitcher Sean Sullivan has recovered from a painful introduction to the Majors in 2026.

Sullivan, the Rockies’ No. 20 prospect per MLB Pipeline, left his June 12 debut against the Athletics at Las Vegas because of illness after three innings.

After the last of his five starts -- July 4 against the Giants -- Sullivan landed on the injured list with a left shoulder injury. All told, he went 0-3 with an 8.87 ERA in 22 1/3 innings, with 16 strikeouts but 11 walks.

After going to the injured list, Sullivan dealt with elbow pain, was given a cortisone shot and didn’t return to competition until three short September appearances for Triple-A Albuquerque.

But Sullivan is rebounding. During the lengthy rehab, Sullivan muscled up his thin, 6-4 frame by about 10 pounds to 200. Assigned to the Arizona Fall League’s Salt River Rafters (1-1, 5.59 ERA in three games), Sullivan is applying the lessons his short, difficult time in the Majors revealed.

“It was in large part fatigue and injury, but the time up there showed me a lot -- it was kind of a wake-up call,” said Sullivan, a second-round Draft pick in 2023 out of Wake Forest. “It showed me what changes I needed to make, whether it be with my body, my pitches, my routine, my workload management and just my arsenal in general.”

In 11 games before the callup from Albuquerque, Sullivan was 5-3 with a 5.60 ERA that was hard to gauge because there were some rocky starts -- typical in Pacific Coast League venues.

But in the Majors, Sullivan struggled with a key issue that’s difficult to prepare for in the Minors -- pitching on four days’ rest consistently, with Major League intensity. In the Minors with Monday being a regular day off, the only time a pitcher goes on four days’ rest is when his turns fall Tuesday and Saturday. Sullivan said discussions with the strength and conditioning program, as well as with the club’s dietician, should help him go from “skinny but strong to filled-out.”

All the physical stuff must translate into fastball velocity.

Going into the Draft and through his Minor League career, Sullivan has succeeded with deception, which made his four-seam fastball difficult for hitters to time. He releases the ball roughly seven feet closer to the plate than the rubber -- a figure that placed him at the top among MLB pitchers in 2026. While such extension made Sullivan’s pitches appear faster, his actual average fastball velocity of 87.5 mph placed him at the bottom among MLB pitchers. He and the Rockies believe he must bring more power.

“That was pretty clear for me – those swings and misses [in the Minors] turned into foul balls, or turned into doubles or harder-hit balls,” Sullivan said. “So that’s one of my main goals this offseason. I’ve been working mechanically and in the weight room.”

The Rockies are contemplating all sorts of ways to structure their pitching staff, which means there could be many games in which Colorado doesn't hand the ball to a starter, see how far he goes, and manage the game from there. It’s possible Sullivan will fit one of those structures without having a regular starter’s workload.

“Just getting to see him was a big part of it -- we didn’t see him until late January or early February,” said Rockies director of pitching Matt Daniels, who was hired last December and through a rough pitching year for the club gained information on each hurler. “When you re-watch his Spring Training games, there was a velocity jump over what he was doing [in 2025]. There was some good work done to his delivery to lean into his superpowers with how he likes to move, and we will continue to do that.

“He’s in a group of guys that we want to keep lengthened out. But is it 1 1/2 times through the order? Is it 2 1/2 times? That remains to be seen. It’s figuring out what the sweet spot is between the length he can give us while maximizing his stuff quality.”

The key beyond velocity is improving and diversifying his pitch mix.

“The cutter has been my new one, and it’s a matter of refining that,” he said. “There were instances when it looked good in the game, but other ones where it just wasn’t consistent. And the two-seam fastball, which was introduced to me after I was called up, will be a big pitch for me -- just having another look from a fastball speed. There were some instances where I saw some success, especially against left-handed hitters, but it was hard to get a complete grasp while trying to compete at that level.

“I’m in a lot better spot now, and I’m trying to continue to build on that progress.”