Coming into the season, I didn’t have very high expectations for Kansas City Royals reliever Daniel Lynch IV. Last year, he posted a perfectly acceptable 3.06 ERA over 67.1 innings, but the underlying statistics (4.53 xERA, 4.76 FIP) suggested that he had good fortune and was due for a rude awakening this year. The southpaw always impressed talent evaluators with his stuff and potential, but he had yet to produce results commensurate with his talent. In 363 innings before this year, Lynch logged
a 4.56 ERA (5.00 xERA, 4.74 FIP) over five seasons. Lynch has one more minor league option remaining, and I figured he was more likely to be on the I-29 Shuttle to Omaha than helping the Royals in the bullpen.
It’s still early, but Lynch has been the most effective reliever in Matt Quatraro’s bullpen. The lefty tossed a scoreless eighth inning in the Royals’ 5-3 victory over the Cleveland Guardians on Tuesday night, lowering his ERA to 1.84 this season. His 0.61 WHIP, 2.22 xERA, and 2.34 FIP are all major improvements over his previous numbers, suggesting that he has earned his sparkling ERA with quality pitching. It’s been a truly impressive start for Lynch and one that the Royals really needed. Carlos Estévez had a disaster outing to start the year and is now out with injury, while Lucas Erceg and Matt Strahm have both had shaky moments to start the season. Lynch has provided much-needed stability and has started receiving higher leverage assignments as a result.
What changes have led to his new success? I looked through Lynch’s Baseball Savant and Fangraphs pages to try to see what is different this season. While we are still in the land of small sample sizes (Lynch has pitched 14.2 innings this year), there are three changes that stand out this year.
More sinker, less fastball
Lynch has changed his pitch mix up each of the last two seasons. In 2025, Lynch threw more sliders than four-seam fastballs for the first time in his career (29% slider, 23% four-seam fastball). He increased his sinker usage (19%) in 2025, but he still threw his four-seamer second-most out of any pitch in his arsenal.
This season, Lynch is still throwing 29% sliders, which is his most-used pitch so far, but has increased his sinker usage to 28%. Against lefties in particular, Lynch has essentially become a two-pitch pitcher; 93% of his pitches against lefties have been either the sinker or the slider. Royals fans know how effective a good sinker and slider combination can be; Brady Singer was an effective major-league starter, particularly against same-handed hitters, with mastery of just those two pitches. Lynch has been death against lefties this year, striking out 9 of the 24 batters he has faced, with an opponent’s average of just .087.
Even against right-handed hitters Lynch is still throwing his sinker more often. His four-seam fastball is down to just 15% of his offerings, which is less often than he throws a changeup and is below his 2025 sinker numbers. I assume the thinking is that the slider is Lynch’s best pitch, and his sinker pairs better with the slider than the four-seam fastball does, therefore more slider and less four-seam will help Lynch get better results. So far, so good.
Higher arm slot, less extension
Lynch has not settled on a consistent arm slot during his career, which presumably has not helped him find consistent results. Last year, the southpaw had the lowest average arm slot of his career at 36 degrees. This season, he has raised his arm slot to 42 degrees.
He also has a lower extension this year than he has had in previous years, which means he is releasing the ball farther away from the plate. The 6’6” pitcher has generally had an above-average extension; last season he was in the 70th percentile for extension. This season, Lynch has released the ball a few inches earlier and farther away from the plate than he has in previous seasons, which places him in the 48th percentile among pitchers.
Generally, pitchers like to get more extension on the ball. The closer you release the ball to the mound, the higher the perceived velocity by the hitters is, because they have less time to react. Bailey Falter essentially has a career because he has such elite extension. Extension is particularly important when you are throwing four-seam fastballs, but can be counter-productive when throwing sinkers. Sometimes heavy sinker pitchers want less extension because they want the ball to have more time to break.
This could be small-sample noise, but if Lynch has made an intentional change with his arm slot and his extension to accentuate the horizontal movement of his pitches, particularly his sinker, then it makes you feel better about his ability to replicate the results he has had so far this season. His sinker has had great horizontal movement both in 2025 and 2026, and his changeup and slider have more average horizontal movement so far in 2026 than they did last year. My suspicion is that Lynch, Brian Sweeney and the rest of the Royals pitching staff (along with any private team that Lynch uses) tinkered with his mechanics in the offseason to emphasize horizontal movement of his pitches. So far everyone should be pleased with the results
Increased sharpness
If I’m right and Lynch tweaked his pitching mechanics in the offseason to help him get the most out of his slider/sinker combination, it has increased his overall effectiveness and sharpness. So far, Lynch has thrown better pitches while retaining the ability to locate the ball. Lynch has struck out 18 batters in 14.2 innings. He’s in the 89th percentile in chase percentage, 98th percentile in whiff percentage while remaining in the 86th percentile in walk percentage. If you can strike guys out and not walk guys as a major-league pitcher, then you are going to find a lot of success.
Stuff+ is a metric developed by Eno Sarris at Fangraphs that looks at the physical characteristics of a pitch (release point, velocity, vertical and horizontal movement, spin rate, etc.) to determine how effective of a pitch it is regardless of results. Lynch has had a below average Stuff+ (92, 100 is average) for his entire career until this season. All of his pitches grade better this season, and his overall Stuff+ number has jumped to 107 this year.
The southpaw has generally been above-average when it comes to locating the ball coming into this season. Even throwing nastier stuff in 2026, he still has above-average command of his pitches, according to Location+. If your pitches get nastier while you keep your ability to locate pitches, which is what Lynch has done this year in a small sample, then you are set up for success as a pitcher.
Relievers are fickle and things can change quickly, but studying the information we have on Lynch makes me think that he has made multiple intentional changes to his repertoire and mechanics, which are leading better results this year. Hopefully, these changes stick throughout the year and give Quatraro another high-leverage option.
