Niko Sullivan’s first taste of the majors came with a crash course attached.
The Rockies’ No. 20 prospect per MLB Pipeline debuted on June 12 against the Athletics at Las Vegas, but illness cut that outing short after three innings. His season never really settled after that.
Following his fifth start on July 4 against the Giants, Sullivan went on the injured list with a left shoulder injury. In all, he finished 0-3 with an 8.87 ERA across 22 1/3 innings, striking out 16 and walking 11.
The damage didn’t stop there. After landing on the injured list, Sullivan also dealt with elbow pain, received a cortisone shot and didn’t make it back into game action until three brief September appearances for Triple-A Albuquerque.
Now, after a long rehab stretch, he’s trying to turn that rough introduction into something useful. Sullivan added about 10 pounds to his thin 6-4 frame and now checks in at 200 pounds. He’s with the Arizona Fall League’s Salt River Rafters, where he’s 1-1 with a 5.59 ERA in three games, and he’s carrying a much clearer sense of what the big-league level demanded of him.
“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.”
Before the callup from Albuquerque, Sullivan had gone 5-3 with a 5.60 ERA in 11 games, a line that didn’t tell the whole story because some of those starts got rocky in typical Pacific Coast League fashion. But the majors exposed a tougher adjustment: pitching every five days, on four days’ rest, with the pace and pressure turned all the way up.
That workload is different from the minors, where Monday is usually an off day and four days’ rest only shows up in specific spots. Sullivan said he has already had talks with the Rockies’ strength and conditioning staff and the club’s dietician, with the goal of going from “skinny but strong to filled-out.”
The physical changes matter because the Rockies believe the stuff has to sharpen, too. Sullivan has built his game on deception, using extension that makes hitters feel like the ball is on them quicker than it really is.
He releases the ball roughly seven feet closer to the plate than the rubber, a mark that ranked him at the top among MLB pitchers in 2026. But the fastball itself sat at 87.5 mph, which put him at the bottom among MLB pitchers.
That gap is why the Rockies and Sullivan both see more power as a necessity, not a bonus.
“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.”
He’s also working to expand what he can throw. The cutter is the newest piece, and Sullivan knows it still needs polish.
The two-seam fastball, introduced after he was called up, is another pitch he expects to lean on more, especially because it gives hitters a different look off fastball speed. But he said it was tough to get a full read on either pitch while trying to compete at that level.
“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.”
Rockies director of pitching Matt Daniels said the club didn’t get a full look at Sullivan until late January or early February after being hired last December. Daniels said a rewatch of Sullivan’s Spring Training outings showed a velocity jump from what he had done in 2025, along with work on his delivery to better use his strengths.
“Just getting to see him was a big part of it -- we didn’t see him until late January or early February,” Daniels said. “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.”
For Sullivan, the next step is obvious: get stronger, throw harder and bring a fuller arsenal with him the next time the Rockies come calling.
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