Is the Curveball Key to a Seth Lugo Turnaround?

[Kevin O'Brien]

Image courtesy of Rick Osentoski-Imagn Images

 

Much has been made about Seth Lugo and his outlook for the 2026 season. For the Royals to have a chance at an AL Central Division title and return to the postseason, Kansas City will need a Lugo closer to his 2024 form than to his 2025 version. 

In 2024, he went 16-9 with a 3.00 ERA, 3.25 FIP, 1.09 WHIP, 3.77 K/BB ratio, and 4.7 fWAR in 206.2 IP. That performance helped him not only earn the Bruce Rice Pitcher of the Year award (which goes to the Royals' best pitcher), but it also garnered him AL Cy Young runner-up honors to Detroit's Tarik Skubal. Thus, after 2024, it seemed like Kansas City had a top-of-the-rotation arm that could complement Cole Ragans for at least a few more seasons.

 

Unfortunately, Lugo took a step back in 2025, much to the Royals' and Kansas City fanbase's chagrin.

Due to various injuries, he only pitched 145.1 innings, and the numbers regressed in that small sample as well. He posted a 4.15 ERA, 5.09 FIP, 1.29 WHIP, 2.27 K/BB ratio, and 0.5 fWAR. Even though the Royals gave him an extension near the end of the season (keeping him in Kansas City until at least 2027), many fans wondered at the end of the 2025 season if Lugo had peaked in 2024 and would be on the decline for the remainder of his career. At 36, he is at an age when such career regression is common.

The 34th-round pick in the 2011 MLB Draft out of Centenary College of Louisiana made his Spring Training debut this season and held his own in two innings of work. He threw 27 pitches and struck out one while allowing two hits, zero runs, and zero walks. Lugo was also efficient with his pitch mix, posting intriguing stuff and strike metrics, according to his TJ Stats summary below.

His overall TJ Stuff+ was just 97, and he only had three pitches with a TJ Stuff+ over 100 and one with a 55 grade (his curveball). He was also a bit inconsistent when it came to finding the strike zone, as illustrated by his 44.4% zone rate. However, his chase rate was 40%, his whiff rate was 28.6%, and his xwOBACON was .327. That's not bad for a first Spring Training start, especially for a veteran who's just trying to ramp up and stretch himself out in preparation for Opening Day.

The results and overall profile of Lugo don't matter too much, especially considering this is just one Cactus League outing. However, his curveball was an interesting offering, even if it was only thrown two times against the Cubs. It's an intriguing pitch to watch this spring, as it regressed a bit in 2025 from 2024, and one could argue that its effectiveness decline partially explains Lugo's struggles a season ago.

Let's take a look at the changes in Lugo's curve, why that's important, and what kind of takeaways Royals fans could have on the pitch from Lugo's 2026 Cactus League debut.

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Lugo's Curve Saw a Decline in Velocity and Pitch Quality

On Monday, Nick Pollack of Pitcher List released his Kansas City Royals SP Breakdown. Pollack breaks down all the rotations of every MLB team before Opening Day, and his SP Breakdown series is one of the best annual deep dives out there for fantasy baseball diehards. Below is a link to Pollack's latest piece, focusing on the Royals' starting pitchers for 2026.

 

As expected, Pollack broke down Lugo and his outlook for 2026. The Pitcher List founder focused on Lugo's curveball and how it changed in 2024, which contributed to his decline in success last season.
 

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I was initially interested in Lugo for 2026, considering his effectiveness early in 2025 until his back began barking, but there was one metric that has me worried: his curveball velocity. It was down two ticks all season. Normally, I wouldn’t care so much about a hook falling to 77 mph from 79 mph, but Lugo’s yakker is his tether to success. The slower velocity led to a massive decline in whiffs, crumbling the putaway rate, and, naturally, his success.

 

Curious by Pollack's comments, I did a TJ Stats summary comparison of Lugo from 2024 to 2025, and below is what that data set looked like.

Lugo saw declines across many metrics last season. His overall TJ Stuff+ went from 99 to 98, and that seemed to contribute to his regression in all his overall categories via TJ Stats. His chase rate increased from 29.3% in 2024 to 23.8% in 2025. His whiff rate went from 22.4% to 20.5%. Lastly, his went xwOBACON went from .363 to .427. The only category where he saw improvement was zone rate, which rose from 48% to 51.1%. That said, while he threw more pitches in the strike zone in 2025, it also made him more hittable. His expected batting average against went from .240 in 2024 to .256 in 2025. 

While many of Lugo's pitches regressed from 2024 to 2025, the curveball trend stood out the most. Here's what the breakdown of the pitch was in both 2024 and 2025, via TJ Stats.

• 2024: 16.2% usage, 79.8 MPH, -14.5 iVB, -14.6 HB, 3,283 spin, 109 TJ Stuff+, 68 grade, 41.9% zone, 41.1% chase, 33.6% whiff, and .367 xwOBACON. 
• 2025: 18.2% usage, 78.9 MPH, -13.8 iVB, -14.4 HV, 3,237 spin, 106 TJ Stuff+, 64 grade, 47.5% zone, 32.5% chase, 25.9% whiff, and .442 xwOBACON. 

Lugo threw the pitch two percent more in 2025 than in 2024. However, nearly everything worsened, except the zone rate. That said, for a pitch that generated so much chase and whiff in 2024, throwing it more in the zone was actually counterintuitive and led to worse results, especially in whiff rate and xwOBACON. 

The key difference seemed to be the decline in velocity. Not only was it 0.9 MPH slower in 2025 than in 2024, but it was also his slowest curveball MPH since 2020, as seen in the chart below via Baseball Savant.

 

In addition to a decline in velocity, Lugo's curve also experienced a decline in spin rate last season. His 3,237 spin was 46 RPM lower than his 2024 spin. Furthermore, like velocity, his curveball spin had the lowest RPM since 2020, as seen in the chart below via Savant.

A decline in spin and velocity often leads to a regression in pitch quality, and that was the case with Lugo's curve last season. His TJ Stuff+ declined by three, and his curveball grade declined by four from 2024 to 2025. Granted, some of it may have been due to injury. A finger injury at the beginning of the year and later a back issue seemed to not only force him to pitch fewer innings but also produce fewer quality outings on the mound. 

It's likely that those two issues also affected his velocity, spin, and the overall quality of his curveball last season, based on the data. 

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What Did the Heatmap Data Look Like From 2024 and 2025?

In order to understand the decline in Lugo's curveball effectiveness, it seemed essential to explore the heatmap data on Lugo's curve from 2024 to 2025. Seeing where the pitch was located and the results against left-handed and right-handed batters could give a glimpse of what went wrong for Lugo last year with his primary breaking pitch. 

Let's explore what his curveball heatmap looked like from last season.

As one can see above, Lugo threw the pitch way too much in the zone, against both lefties and righties. He produced decent CSW rates, with a 32.2% mark against lefties and 33.7% against righties. Furthermore, his whiff rates were solid as well: 25.5% against lefties, 27.3% against righties. However, when opposing hitters made contact, they did damage. He allowed a .462 xwOBACON against lefties with his curve and a .374 mark against righties. 

Here's an example of Lugo leaving up his curveball in the zone against right-handed hitter Marcell Ozuna. He absolutely punishes it for a home run at Kauffman Stadium in late July. 

Now, let's take a glance at his curveball heatmap data from 2024, via TJ Stats.

The curveball against lefties is pretty much located in the same area as 2025. However, the results were much better: the CSW was 4.3% better, the whiff rate was 7.5% higher, and the xwOBACON was 79 points lower. The better pitch velocity and spin likely helped in 2024.

That said, the curveball results were dramatically better against righties in 2024 than in 2025.

While his CSW was 2.1% lower than in 2025, his whiff rate was 10.2% higher, and his O-Swing% was 14.7% higher as well. He didn't get as many called strikes with the curve against righties, but he generated WAY more whiffs and chase. Furthermore, he located the pitch much differently against righties in 2024 than in 2025. In 2024, he commanded the pitch more low and away, which explains not just the better chase and whiff rates, but also the better xwOBACON (.263). 

Below is an example of Lugo getting San Francisco's Tyler Fitzgerald to strike out on a curveball located low and away, right in the heart of the heatmap. 

A key for Lugo will be locating the pitch more effectively against righties in 2026. He doesn't throw the curve much against righties, only throwing the breaking offering 9.1% in 2025 and 4.0% in 2024. However, while limited, location matters. If he's going to use it under 10% against right-handed hitters again in 2026, he'll need to do a better job of commanding it low and away, like in 2024, not high and in the middle, like in 2025. 

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What to Watch From Lugo's Curve This Spring

Velocity and spin will be the key to success for Lugo and his curveball in 2026. Even when he didn't have the best velocity on his curveball in 2024, it was a much sharper offering than the loopier one he threw last season. In the clip compilation below, the 2024 version against Andres Gimenez is a much steeper dropping pitch than the 2025 one against Miami's Kyle Stowers. This is despite the 2024 curveball being 0.5 MPH slower.

Getting that spin and vertical break again on the curve for Lugo will be key this spring. Thankfully, it seems like he's making progress on at least some of his breaking offerings in Spring Training. MLB.com Royals writer Anne Rogers noted that Lugo added two MPH to his slider in his first outing, thanks to some grip changes made this offseason. 

 

In addition to four whiffs, Lugo produced a 60% zone and 50% chase with the slider. And yet, the slider had a 101 TJ Stuff+ and a 45 grade today. That is slightly worse than the 102 TJ Stuff+ and 55 grade on the curve from today's outing. Yes, he threw the slider five times and the curve twice. However, if he's being that intentional with his grip and mindset on the slider, it's likely he's adopting the same approach with his curve, which is a more crucial pitch to his repertoire. 

If a similar trend with his curve happens in subsequent outings this spring, whether in Arizona or the World Baseball Classic (he will be pitching for Puerto Rico), then the 36-year-old righty may be on his way to recapturing some of the magic of his 2024 campaign for this upcoming season.

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