Major League Baseball teams are continuously searching for innovative strategies to maximize the potential of their rosters and extract the most value from their players. One notable trend that has emerged over the past two seasons has been the conversion of certain relief pitchers into starting pitchers. Pitchers such as Garrett Crochet, Reynaldo Lopez, and Jordan Hicks have experienced varying levels of success upon transitioning to the starting rotation, while players such as A.J. Puk and DL Hall struggled upon their attempted transitions out of the bullpen.
The primary incentive behind transitioning relievers into starters lies in the opportunity for these pitchers to handle increased innings, thereby providing their teams with valuable additional innings volume. Given the frequency of pitcher injuries and the difficulty of maintaining pitching depth throughout the season, a successful bullpen-to-rotation conversion can significantly boost a player’s contribution to their team and generate a higher total WAR, even if some peripheral metrics, such as strikeout rate, decline slightly. The optimal outcome is a pitcher who maintains his level of effectiveness despite the heavier workload, as the Chicago White Sox did with Garrett Crochet, creating an attractive trade asset that the organization later used to acquire additional prospects, spearheading their rebuild.
However, the transition from relief to starting rotation is not straightforward. It demands a baseline level of command and pitch arsenal versatility sufficient to effectively face opposing lineups multiple times per game. Typically, pitchers find themselves in relief roles precisely because they lack the command or diverse pitch mix necessary to sustain prolonged effectiveness in a starting role. This past offseason, multiple organizations identified Clay Holmes as a potential reliever-to-starter conversion candidate, and the New York Mets signed him to a 3-year, $38M contract this offseason with the intent of utilizing him as a starting pitcher.
Despite not starting a Major League game since 2018, Holmes has generated above-average Location+ grades over each of the past two seasons and displayed a willingness to further develop his pitch arsenal to add offerings that could be used to more effectively face left-handed hitters. This article will explore the specific changes that Clay Holmes made to his pitch arsenal this offseason, and evaluate how these adjustments may enable him to thrive as a full-time starter this season.
Overview
Making his debut during the 2018 season with the Pittsburgh Pirates, Holmes spent his first three and half seasons in the Majors with Pittsburgh until being traded to the New York Yankees in July of 2021. After being named the Yankees closer at the start of the 2022 season, Holmes accumulated 74 saves as the Yankees closer before filing for free agency after last season. While Holmes was dominant against right-handed hitters in 2024, he displayed a decline in performance against left-handed hitters last season, particularly as it pertained to his strikeout rate.
As shown by the table above, Holmes produced a 31.6% strikeout rate, 7.4% walk rate, and 24.3% K-BB against right-handed hitters last season, while against left-handed hitters he produced an 18.5% strikeout rate, 8.5% walk rate, and 9.6% K-BB. I wrote about these wide platoon splits that Holmes experienced last season, and these issues against left-handed hitters ultimately led Holmes to lose the closer role towards the end of last season in favor of Luke Weaver. Holmes relied on his sinker 63.2% of the time last season to left-handed hitters, and while the pitch’s outlier vertical drop still allowed for Holmes to generate ground balls on the offering (72.9% ground ball rate to left-handed hitters against the sinker last season), this allowed for left-handed hitters to anticipate the offering and produce hard contact.
To successfully make his transition to the starting rotation, Holmes needed to improve his platoon splits to improve his effectiveness against left-handed pitchers. While his sinker is effective at generating ground ball contact against hitters of both handedness, sinkers are typically not platoon-neutral offerings and Holmes was a candidate to add a second fastball to his pitch arsenal. In addition, Holmes did not feature an off-speed pitch in his arsenal, making him a prime candidate to add a changeup to his pitch arsenal. Over the offseason, Holmes went to Tread Athletics and worked to make adjustments to his pitch arsenal that would make him more effective against left-handed hitters.
Arsenal Changes
The tables above depict Holmes’s short-form movement plots from the 2024 and 2025 seasons. As shown by the plots above, Holmes added three pitches to his pitch arsenal this season: a cutter, a changeup, and a four-seam fastball. The new cutter allows him to utilize an additional fastball to left-handed hitters, the new changeup provides him a swing-and-miss offering to utilize to left-handed hitters, while the sparingly used four-seam fastball provides him with a third fastball he can utilize to opposing hitters to “keep them honest”. These three pitches were added to Holmes’s arsenal with the deliberate intent to improve his performance against left-handed hitters, an objective that is imperative to Holmes’s successful transition from the bullpen to the starting rotation.
The table above contains the pitch quality grades of the six offerings in Holmes’s arsenal, as measured by four notable pitch quality models (FanGraphs’s Stuff+, PLV, my aStuff+ model, and PitchingBot). The models agree that the changeup is an above-average offering, while the models disagree slightly on the quality of Holmes’s cutter. All four models agree that Holmes’s four-seam fastball displays below-average shape. (Please note that FanGraphs’s Stuff+ and PitchingBot do not differentiate between sliders and sweepers).
Utilizing multiple fastballs has been an emerging trend among Major League pitchers over the past couple of seasons. By incorporating multiple fastballs, pitchers leverage the varying movement profiles of each pitch, forcing hitters to differentiate between them rather than comfortably timing a single predictable shape. This ties into the concept of arsenal effects, which was covered extensively by Stephen Sutton-Brown of Baseball Prospectus over the offseason, which attempts to measure how well pitches look similar to each other. I would expect that these three fastballs interact well with each other, which will allow for these pitches to perform above their pitch quality grades moving forward.
In my opinion, the most significant change to Holmes’s arsenal this season has been the introduction of the changeup to his arsenal. Holmes’s changeup is a “kick change“, a new type of a changeup that has become popular throughout Major League Baseball since Hayden Birdsong and Davis Martin began throwing it towards the end of the last season. Popularized by Leif Strom at Tread Athletics, the kick change utilizes a spiked changeup grip, allowing for the middle finger to “kick” the pitch’s spin axis, generating more vertical drop than a typical changeup. Similar to the rise in the splitter last season, the introduction of the kick changeup is a particularly important development for pitchers that exhibit supination bias, as these pitches don’t require the same amount of pronation that a traditional changeup grip necessitates, allowing for them to develop an off-speed offering to utilize against hitters of the opposite handedness that fits within their natural biases.
As a pitcher who exhibits supination bias (a natural tendency to get on the outside of the baseball) given his ability to throw a breaking ball at high velocity and possessing low spin efficiency on his fastball, Holmes was a prime candidate to add a kick changeup over the offseason. Averaging 87.7 MPH, the pitch generates roughly 0 inches of induced vertical break and 15 inches of arm-side run, resulting in all four pitch quality models grading the pitch as above-average. While it is too early to place much emphasis on the results of the offering, the pitch is currently generating a 31.6% whiff rate when utilized to left-handed hitters.
As shown by the table above, these changes to Holmes’s pitch arsenal have resulted in a change in how he utilizes his offerings to left-handed hitters. As mentioned earlier, Holmes utilized his sinker 63.2% of the time to left-handed hitters, which is down to 16.4% so far this season. Holmes predominantly utilizes his new cutter and changeup against left-handed hitters (utilizing both pitches a combined 47.2% of the time), while these offerings are utilized sparingly to right-handed hitters. Holmes’s pitch usage against right-handed hitters has largely remained the same in 2025, with Holmes slightly increasing the usage of his sweeper and decreasing the usage of his tighter slider, while Holmes has proceeded with a “kitchen sink” approach when facing left-handed hitters. Overall, Holmes’s revamped pitch arsenal provides him with better tools to effectively attack left-handed hitters, and I expect that his performance against opposite-handed hitters to significantly improve this season compared to the results he displayed in 2024.
Concluding Thoughts
The main question to this article is, will Clay Holmes successfully make the conversion to the starting rotation? While it is too early to give a definitive answer to this question, the results look optimistic so far and I am hopeful that Holmes will be able to finish the season as a front-half of the rotation starter for the New York Mets. The main piece of information that I am looking at for the remainder of the season is whether Holmes will be able to maintain his current level of velocity throughout a full season. Garrett Crochet was able to maintain a 97.1 MPH average fastball velocity over 146 innings pitched last season, while Jordan Hicks’s average fastball velocity decreased from 100.1 MPH as a reliever in 2023 to 94.5 MPH as a starter in 2024.
After averaging 96.6 MPH on his sinker in 2024, Holmes is currently averaging 93.7 MPH on his sinker in 2025, with his sweeper and slider also experiencing a decrease in velocity as well. A small decline in velocity can be expected when transitioning to the starting rotation, as facing more hitters during an outing de-incentives pitchers from pitching at “max-effort” as they would coming out of the bullpen. Keeping a close eye on Holmes’s average velocity will be an important benchmark of how well his transition to the rotation will turn out, as Holmes’s arsenal would look a lot different if each pitch continued to lose additional ticks of average velocity throughout the season.
Last week, Nate Schwartz wrote that Jack Leiter was the epitome of modern pitching, and I would contend that Clay Holmes makes a solid argument for this moniker as well. Holmes added a sweeper to his pitch arsenal at the beginning of the sweeper revolution, throws a deathball-shaped slider, utilizes multiple fastballs, and has added a kick change to his arsenal as the pitch has grown in popularity across the league. The next trend that Holmes is attempting to conquer is to be able to transition from closer to starting pitcher successfully, and I believe that as long as his velocity can hold over the course of the season, the changes he has made to his pitch arsenal to better perform against left-handed hitters embodies the art of becoming an effective starting pitcher at the Major League level.
Photos by Icon Sports Wire and Adobe Stock | Adapted by Carlos Leano
