The 2023 seventh rounder made his MLB debut in August with a one pitch, one out performance
20. Seth Halvorsen (293 points, 21 ballots)
Halvorsen spent his first year or so in professional baseball on a rocket path up the minor-league ladder. The nearly 25-year-old righty reliever was the first member of the Rockies’ 2023 draft class to reach the big leagues in late August 2024, less than 14 months after the Rockies picked him in the seventh round last year out of Tennessee to join his college teammate Chase Dollander and gave him an under-slot $200k bonus.
It was a more windy road for Halvorsen before his success in the minor leagues. He was a two-way prospect who had Tommy John surgery early in his freshman year at Missouri, then played some center field during the shortened pandemic year in 2020. Once he was healthy enough to return to the mound in 2021, Halvorsen was exclusively a starting pitcher whose wildness mitigated his effectiveness. It took a transfer to Tennessee for him to develop significantly as a multi-inning reliever through 2023, including additions of a slider and splitter to his pitch arsenal.
Atypically for most pitching draftees of late, Halvorsen threw 13 1⁄3 innings in his draft year, making appearances in the ACL, High-A, and Double-A. In 2024, the 6’2” pitcher was assigned to Hartford to begin the year at a slightly below league average age. In 33 appearances with Hartford, Halvorsen had a 4.84 ERA with a 1.50 WHIP, 10.4 K/9 rate, and 4.8 BB/9 rate. The Rockies promoted him to Albuquerque in early August, where despite the higher competition level and tougher offensive environment, Halvorsen thrived. In eight appearances with Albuquerque, Halvorsen threw eight innings, allowing three runs on eight hits and four walks while striking out 15 batters.
That was enough for the Rockies to select Halvorsen’s contract in late August — he made his Major League debut on August 30th with a one pitch, one out performance. That was the beginning of a very successful stretch to start Halvorsen’s MLB career. In all, Halvorsen appeared in 12 games with the Rockies, allowing only two earned runs on eight hits and two walks with 13 strikeouts in 12 1⁄3 innings while throwing triple digit heat. He got three save chances down the stretch, converting two of them and blowing one in memorable fashion to two of the best hitters in the league. Halvorsen’s 0.6 rWAR for the year ranked T-13th among all Rockies and T-6th among pitchers.
Here’s some video of Halvorsen’s MLB highlights from 2024:
Eric Longenhagen of Fangraphs gives Halvorsen a 40+ FV grade and ranks him 13th in the system with a plus plus slider and plus fastball:
All three of Halvorsen’s pitches can be nasty. Because he lacks precise command, both of his secondary pitches have a tendency to finish all over the place. His slider, which averaged 88 mph during Halvorsen’s big league trial, is hard enough to miss the barrel even when it backs up, and some of his mis-released splitters act like two-seamers running off the front hip of lefties and catching the corner. Fernando Cruz, Scott McGough and Erik Swanson are fair present comps for the way Halvorsen is likely to operate, with his pitch usage spread across his whole mix so that unpredictability can help him get away with his mistake locations. He profiles as the third- or fourth-best reliever in a good bullpen, one who has experience getting more than just three outs and who has the pitch mix to do so.
In the recent Baseball Prospectus system write-up, Halvorsen is ranked 11th:
Blessed are the gas-throwers, for they shall inherit the workload. Halvorsen beat his college teammate Dollander to the bigs, debuting last year and earning a couple saves late in the season, courtesy of a wide open Colorado bullpen and a fastball that sits triple-digits. Atypically for a fireballer of his caliber and bullpen profile, Halvorsen actually mixes in four distinct pitches, with a sinker, split-change, and slider all pairing off his four-seamer. The splitter is my favorite of the secondaries, with a tight fading profile and velocity separation that can stymie hitters on both sides of the dish. In a more fleshed out bullpen, Halvorsen would get the chance to work lower leverage innings for longer, but in a young Rockies group he could easily become the top high-leverage option.
Given his success to end 2024 and health permitting, Halvorsen seems like a lock to exhaust his PuRP eligibility within the 2025 season’s first month as one of the top relief options for the Rockies. Even though I generally discount relievers due to their role’s limited impact, that profile is plenty worthy of the 40+ FV grade I gave him on my list, 18th in the system.