David Cooper | March 12, 2026
On Sunday the Colorado Rockies optioned pitchers Welinton Herrera, Carson Palmquist, and Luis Peralta to their Triple-A affiliate — the Albuquerque Isotopes. Typically, sending three young arms back to the minor leagues halfway through Spring Training would go completely unnoticed. However, this move came as a surprise because Herrera, Palmquist, and Peralta are all lefties, which leaves Brennan Bernadino as the lone lefty reliever on the active roster.
Of the remaining right-handed bullpen pieces, few had success against lefties a season ago. Last year, the MLB average RHP v. LHH in walks + hits per innings pitched (WHIP) was 1.37. The recently acquired Pierson Ohl (1.27 WHIP) is the only 2026 right handed bullpen piece with above average reverse splits in 2025: Jimmy Herget (1.40 WHIP), Seth Halvorsen (1.50 WHIP), Jaden Hill (1.66 WHIP), Juan Mejia (1.67 WHIP), Victor Vodnik (1.78 WHIP), Antonio Senzatela (1.81 WHIP), and Zach Agnos (1.86 WHIP).
We cannot expect Brennan Bernadino to come in and face every lefty hitter late in the game for the 2026 Rockies — and neither do the Rockies pitching coaches.
By analyzing how the right-handed relief arms are approaching lefty hitters in the first few weeks of Spring Training, it becomes clear that a change in arsenal and usage against lefties has left the Colorado Rockies’ front office confident in their ability to retire lefty hitters.
Antonio Senzatela: Moving Away from the Four-Seamer
For years, Antonio Senzatela has leaned heavily on his four-seam fastball. This spring, however, the pitch mix is shifting.
Four-seam usage against lefties has dropped dramatically, from 60% last season to 38% this spring. In its place, Senzatela is leaning more heavily on two secondary offerings.
His curveball usage has nearly doubled (16% to 30%), and the early results suggest it is becoming a legitimate chase pitch. The curve has generated a jump in chase rate from 28% to 40% and whiff rate from 27% to 50%.
Meanwhile, the changeup is being used more intentionally in two-strike counts, increasing the use of the change 17% in two-strike counts, rather than 2% compared to last year. Simultaneously, it is being thrown in the strike zone far more often (38% to 71%).
The adjustment suggests a clear shift in philosophy: rather than challenging lefties with fastballs, Senzatela is trying to create weak contact in the zone with the changeup and induce swing-and-miss with the curve.
Jaden Hill: Introducing the Slider
Jaden Hill may be showing the most dramatic arsenal change so far.
Last season, Hill relied heavily on his changeup, throwing it 44% of the time to lefties. This spring, that number has dropped to 28%, largely because a new pitch has entered the mix: the slider.
Slider usage has jumped from 4% to 26%, and early results are striking. The pitch is generating 43% chase and 50% whiff rates, immediately giving Hill a swing-and-miss option against opposite-handed hitters.
If the slider holds up against stronger competition, Hill may have found a true put-away pitch against left-handed hitters.
Jimmy Herget: Sweeper over the Curve
Jimmy Herget is undergoing a more structural pitch mix change.
His curveball usage versus lefties has dropped from 29% to 11%, replaced by a newly introduced sweeper that now accounts for 21% of his pitches to lefties.
The early returns show the sweeper being thrown confidently in the strike zone — 60% zone rate and 60% strike rate — suggesting it may function more as a contact-management pitch by landing it away to lefties, than a chase weapon.
At the same time, Herget is reshaping his fastball profile. His sinker usage has fallen (26% to 13%), while four-seam usage has doubled (10% to 21%).
The changes hint at a broader approach shift: moving toward horizontal movement with the sweeper while using the four-seamer more aggressively against lefties.
Juan Mejia: Doubling Down on the Fastball
While many pitchers are experimenting, Juan Mejia is doing the opposite.
Mejia already relied heavily on his four-seam fastball against left-handed hitters last season, and that trend has continued. Fastball usage remains extremely high, sitting at 77% this spring compared to 79% last year.
The pitch worked well in 2025, holding lefties to a .745 OPS, and the early results this spring are even more encouraging.
Whiff rate on the four-seamer has jumped dramatically from 20% to 58%, while balls in play have dropped from 18% to just 3%.
Meanwhile, slider usage has fallen from 20% to 8%. In contrast with the fastball, lefties thrived on the slider (1.017 OPS in 2025), further reinforcing the idea that Mejia is leaning into the pitch that already works best for him.
Seth Halvorsen: Rebalancing the Arsenal
Seth Halvorsen is making multiple adjustments at once.
Most notably, he has reduced his splitter usage from 36% to 19%, while increasing slider usage from 5% to 17%.
The slider is now appearing more frequently early in counts, with first-pitch usage increasing from 17% to 27%. The pitch has also been extremely effective so far, posting: 83% zone rate, 83% strike rate, 100% chase rate, and a 67% whiff rate.
Late in counts, however, Halvorsen is turning to the four-seamer more often. Two-strike fastball usage has climbed from 44% to 69%, though the early results have not been encouraging, with a 2.750 OPS allowed this spring against lefties with the fastball.
That dynamic may be something to watch as the season approaches.
Victor Vodnik: Too small a sample
Victor Vodnik has thrown only eight pitches to left-handed hitters this spring, making it difficult to draw meaningful conclusions.
What is worth watching, however, is whether he begins moving away from his four-seamer. Last season, left-handed hitters posted a 1.032 OPS against the pitch.
If adjustments are coming, they may involve heavier reliance on his changeup, which was far more effective, allowing just a .368 OPS versus lefties in 2025.
Zach Agnos: Shifting Away from the Splitter
Zach Agnos appears to be correcting an issue from last season.
In 2025, his splitter was overused despite poor results, allowing a 1.047 OPS against left-handed hitters. His four-seam fastball, meanwhile, was far more effective with a .702 OPS allowed.
This spring, the usage is beginning to reflect that.
Four-seam usage has increased from 31% to 39%, with an especially large increase in two-strike situations (27% → 46%). Accordingly, splitter usage has dropped from 35% to 26%.
If the adjustment sticks, Agnos may be aligning his pitch mix more closely with what actually worked last season.
The Bigger Picture
With a new pitching coaching staff in place, these early shifts suggest a deliberate effort to optimize arsenals and usage to empower the right handed bullpen arms to be effective against lefty opponents.
It is still early — Spring Training samples are tiny — but the early signs point to a Rockies pitching staff that may look meaningfully different in 2026.
Written by David Cooper.
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