Corbin Burnes is Not an Ace Anymore
An Analytical Deep Dive into His Regression and What It Means for His Free Agency
Corbin Burnes has become one of baseball’s top starting pitchers. Drafted in the 4th round, Burnes spent most of 2018-2020 as a reliever, pitching only 146 innings. He showed flashes of potential with a high strikeout rate (11.8 strikeouts per nine innings), but his 4.48 ERA during that time suggested some inconsistency. Things took a big turn during the shortened 2020 season when Burnes made his cutter his go-to pitch. By 2021, with its above-average velocity, sharp movement, and pinpoint command, the cutter became his signature weapon and one of the most feared pitches in baseball.
Burnes relied on a mix of his cutter, curveball, and changeup in 2021, dominating the league and winning the NL Cy Young Award with a 2.43 ERA, 1.63 FIP, and 0.94 WHIP. His cutter’s stats were insane: a 32% whiff rate , a 31% put-away rate, and a .199 expected batting average (xBA) with a .290 expected slugging percentage (xSLG). It even had a +20 run value on Baseball Savant. Some argued that hitters were struggling with the pitch because it was so unique—no one had really seen anything like it since Mariano Rivera’s Hall of Fame cutter, but Burnes was throwing his in the mid-to-upper 90s.
In 2022, Burnes experienced slight regression, which was expected. His numbers dipped to a 2.94 ERA and 10.8 strikeouts per nine innings, but he was still among the league’s best, finishing 7th in Cy Young voting.
Things became more concerning in 2023 and 2024. His ERA rose to 3.39 in 2023 as his velocity dipped, but after getting traded to the Orioles, he seemed to bounce back in 2024, posting a 2.92 ERA. Despite recovering his velocity, Burnes' strikeout rate continued to drop—from a league-leading 12.6 K/9 in 2021 to just 8.4 K/9 in 2024. This drop in strikeouts raises questions: what exactly is going on?
In this article, we’ll dive into Burnes’ cutter, examining why it’s no longer generating as many whiffs. We’ll also explore his curveball, changeup, and other secondary pitches to understand why the soon-to-be 30-year-old Burnes is still a desirable free agent while also considering the warning signs that might make teams hesitate.
The Cutter
Corbin Burnes’ cutter has been the cornerstone of his success, but recent trends suggest that its effectiveness is in decline despite its velocity remaining consistent. In 2021, Burnes’ cutter averaged 95.2 mph, and by 2024, it had even ticked up to 95.3 mph but this has not helped stop the trend of his declining whiff rates. The cutter’s whiff rate has steadily dropped, from 32.1% in 2021 to 19% in 2024. It could be the reason for this is hitters simply adjusting to the pitch but I believe there is more to it. There have been some slight movement changes with the (pitch) as well. In 2021, Burnes' cutter had 4.2 inches of horizontal break, but by 2024, it had shrunk to just 2.4 inches.
Max Bay’s Dynamic Dead Zone, which measures how a pitch moves versus how batters expect it to move based on arm angle and other factors, shows that Burnes’ cutter in 2021 had far more lateral movement than hitters were prepared for, making it incredibly deceptive. By 2024, the pitch’s movement became a bit more predictable.
This loss of horizontal movement may correspond with an increase in induced vertical break (IVB). Burnes’ cutter had 11.2 inches of IVB in 2021, which increased to 12.5 inches in 2024. It could be that Burnes changed his grip on his cutter to one where he could generate more velocity on the pitch while killing some horizontal break. This is not a bad idea considering velocity and IVB almost always produce better results as shown in the chart below. But for Corbin Burnes the pursuit of this could have caused him to lose the unicorn shape of the pitch and made it more predictable.
To help visualize these changes, Carter Kessinger’s MLB Pitch Trajectory Viewer is a useful tool. This Shiny app simulates how a pitch moves in real-game settings, and you can see how important the cutter’s shape is to Burnes’ success. At first glance, the differences between his 2021 and 2024 cutters seem minor, but a closer look shows key changes. In 2021, the pitch had great depth and sweep, almost resembling a slider but thrown in the mid-to-upper 90s. That same shape held up in 2022 and 2023, even as the velocity dropped. But in 2024, when Burnes regained his velocity, the cutter lost its depth and sweep, making its movement more predictable. This predictability likely contributed to the statistical decline.
The regression shows up in the numbers. In 2021, hitters managed just a .237 batting average against the cutter, with a .255 expected weighted on-base average (xwOBA) and a .290 expected slugging percentage (xSLG). By 2024, those numbers had increased to .251 BAA, .308 xwOBA, and .390 xSLG. So, what’s going on here? How can Corbin Burnes reclaim the dominance of his 2021 cutter? It’s a tough question because, by some metrics, Burnes’ cutter was actually better in 2024. Its Baseball Savant run value was two points higher than the year before, thanks to a slight velocity increase, and it also had a higher Stuff+ score. However, traditional and expected stats and chase and whiff rates—were at career lows. Ideally, he could regain his 2021 cutter movement while maintaining his 2024 velocity. But if health or mechanics prevent him from throwing that exact pitch, continuing with his current version is still a strong option. The 2024 cutter remained effective, though to maintain his strikeouts and overall whiff rate, he’d need to rely more on his secondary pitches. In 2024, Burnes reduced his cutter usage to 45%, its lowest level since 2021, and shifted more toward his curveball and slider while also introducing a sweeper in the last month of the season.
The Curveball
Corbin Burnes' curveball has been his primary whiff pitch since 2021. During his Cy Young season, he used it effectively by tunneling it off his cutter, achieving an impressive 50.3% whiff rate. In 2024, he used it more frequently than ever, with a career-high usage of 22%, paired with the most drop since 2021 at -15.5 inches of induced vertical break (IVB). While the pitch still generated a solid 37.8% whiff rate, it pales in comparison to his 2021 rate and his 2022 rate of 47.7%. Even in his “worst” season of 2023, the curveball reached a career-high 49% whiff rate, suggesting that the tighter shape of previous years may have been more effective. Additionally, its BAA and run value both hit career lows in 2024, signaling another point of regression for Burnes.
The Slider and Sweeper
Corbin Burnes' slider and sweeper is where we see the first positive trend from his 2024. He increased his slider usage from 8% in 2023 to 15%, making slight adjustments that led to its best performance since 2021 across several metrics. The slider achieved a +3 run value, its highest since 2021, along with its lowest opponent slugging (.196) and batting average against (.286) since then. The expected batting average (.185) and expected slugging (.286) were equally impressive, and its whiff rate jumped significantly to 46.3% from 34.3% in 2023. The pitch also gained more movement, with -1.1 IVB and 8.3 HB in 2024, compared to 0.7 IVB and 7.1 HB in 2023, resulting in increased sweep and drop. A look at his heatmaps shows a key improvement: whereas in 2023, he often left the slider up against lefties, in 2024, he consistently located it low or below the zone to both left- and right-handed hitters.
Burnes introduced a sweeper in 2023, throwing it only 140 times, yet it delivered an impressive 53% whiff rate. With over 17 inches of sweep and an average spin rate close to 3,000 rpm, the pitch showed flashes of elite potential. Although he threw it just 54 times in 2024, he increased its usage toward the end of the season. If his cutter and curveball continue to regress, the sweeper could become a key weapon for him next year. Burnes, a natural supinator with high spin rates, has access to a range of breaking ball shapes, allowing him to manipulate these pitches effectively. Leveraging his ability to generate spin, he would benefit from increasing his breaking ball usage and even experimenting with new variations.
The Future
The question now is how teams will value him as a free agent going into the 2024 offseason. His agent, Scott Boras, is undoubtedly marketing him as an ace who can anchor a rotation for years to come, and this isn't entirely untrue—even in a down season by many metrics, he’s still likely a top-10 pitcher in baseball. However, it's impossible to ignore his downward trend since 2021, culminating in 2024 with career lows in whiff and chase rates, strikeouts per nine innings (K/9), and career-high barrel rates, also not to mention having a career high .347 SLG against him and a .371 xSLG, indicating he should have gotten hit a lot harder than he did. His cutter, once a dominating pitch, has also become more predictable in its movement.
At this stage in his career, making drastic changes to reverse this trend seems unlikely. If Burnes continues regressing at this rate, particularly in key areas like strikeout and whiff rates, he may soon struggle to maintain MLB-caliber performance. Most concerning is his diminishing cutter unpredictability. This pitch has been his defining weapon, elevating him from a solid pitcher with a strong secondary arsenal to an elite, almost unicorn-like talent. Without it, he risks being viewed as less than the ace he was marketed to be.
Conclusion
Corbin Burnes has solidified himself as one of baseball's premier starting pitchers, but his recent trends raise questions about his future value. Drafted in the fourth round, he initially emerged as a high-strikeout reliever before transitioning to a dominant starter, relying on his unique cutter to win the 2021 Cy Young Award. His cutter's sharp movement, high velocity, and consistent command made it one of the league's most effective pitches, placing Burnes among the league's elite.
Since his peak, Burnes has faced new challenges. His cutter, though still fast, has lost some of the movement that once made it nearly unhittable, leading to declines in both whiff and chase rates. While his curveball and slider have shown promise, with solid whiff rates and improved command in 2024, his overall effectiveness has waned, partly due to reduced unpredictability and hitters adjusting to his pitches. The introduction of a sweeper shows potential, yet his primary weapon—the cutter—remains less effective, limiting his strikeout ability and raising questions about his adaptability for sustained success. To his credit, Burnes has demonstrated some adaptability, introducing the sweeper in 2023 and re-integrating it late in the 2024 eason, as well as experimenting with tweaks to his cutter.
Despite these concerns, Burnes is still a valuable pitcher, but teams should be cautious in their investment. Given his recent regression, particularly in his signature pitch, and his age, I would not recommend signing him for more than 2-3 years. This approach would provide a high-upside pitcher while limiting long-term risk should his performance continue to decline. In short, while Burnes brings experience and skill, his trends suggest a tempered approach is wise as he enters free agency.
Big thanks to @McLovinOC8, @james_schiano, @alvarezmet4life, @ckessinger44, @TJstats, and @TimStats for helping directly or indirectly in my research for this project. Follow them all.
And big shoutout to Baseball Savant and Pitcher List (@PitcherList) (@tangotiger). Both incredible sites that helped me a ton.