Ryne Nelson of the Arizona Diamondbacks stepped forward and produced a solid season in 2024. After struggling in his first full season as a starter in 2023, Nelson proved to be one of the more valuable starting pitchers in baseball in the second half of the season, posting a 3.23 ERA. Nelson has always graded out favorably by Stuff+, but the results lagged behind. In a season when the Diamondbacks suffered a myriad of injuries to their rotation, Ryne Nelson proved to be their best at certain times. Further, he was one of the biggest improvers in FIP from last season to this season, which is a positive indicator of his success. Let’s look into how he achieved his success.
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Could Ryne Nelson Have the Makings of a Future Ace?
Fastball Reliance
When Nelson debuted in 2022, he flashed signs of a high-quality four-seam fastball grading out at 120 Stuff+, meaning it was 20% better than the average fastball. Moreover, it possessed excellent characteristics including some of the best vertical ride among all pitchers. Combined with solid velocity at 94.8 MPH, Nelson heavily relied on the pitch, using it nearly 70% of the time. That over-reliance on his best pitch worked in a very small sample of 18 innings. Along with his high-ride fastball, he used a slider that graded out even more favorably at a 129 Stuff+. A high-quality fastball and slider that you can command is an excellent starter kit for a starting pitcher. Altogether, he looked to build on these encouraging signs heading into 2023 expecting to be a part of the rotation.
Nelson made the Opening Day rotation in 2023 and mightily struggled that season. Among pitchers who pitched at least 140 innings, Nelson was the 7th worst according to fWAR. Furthermore, one of the best predictors of pitcher performance is simply looking at a pitcher’s ability to strike batters out and control walks in K-BB%. In this case, Nelson was the third worst in this statistic as well. Nevertheless, he continued to use his fastball at a high rate of 54.6%, but he saw the quality on his fastball and slider regress.
- 2022 Fastball Stuff+: 120 -> 2023 Fastball Stuff+: 102
- 2022 Slider Stuff+: 129 -> 2023 Slider Stuff+ ->: 106
The fastball, in particular, maintained roughly the same velocity but lost over 1.5 inches in vertical movement. The degradation of stuff combined with the elevated usage resulted in the pitch getting crushed with a .554 xSLG and .553 actual SLG. It was a disappointing season that had Nelson’s future rotation spot up in the air.
Second Half Breakout?
In the first half of 2024, it was much of the same for Ryne Nelson. He pitched near a 5.00 ERA, continuing to struggle with missing bats and posting a poor 10.3% K-BB% (around 14% is average). Then, a switch flipped after the All-Star Break. After being well below a 20% strikeout rate for all of 2023 and much of 2024, Nelson’s strikeout rate spiked to 26.6% in the second half. That impressive mark combined with his above-average control placed him in the top 20 pitchers in K-BB%.
Nelson’s first-half pitch usage tendencies did not stray too far from what he had done in the past. Interestingly, he ticked up his cutter usage to 21.5%, which was by far his worst pitch by Stuff+. But he was primarily still throwing his fastball with a variety of breaking and off-speed pitches off of it. His pitches for the most part held the same stuff quality as his poor 2023 season. Post All-Star Break, his stuff quality made a vast improvement and his results corresponded. Here are some notable changes from the first to the second half:
| First Half | Second Half | |
| Four-Seam Fastball Stuff+ | 102 | 109 |
| Slider Stuff+ | 108 | 114 |
| Changeup Stuff+ | 104 | 114 |
| Cutter Stuff+ | 75 | 82 |
| xwOBA | .336 | .285 |
| SwStr% | 9.4% | 9.5% |
These four pitches improving in stuff quality is very encouraging. In addition, he limited the use of his curveball and eliminated using his sweeper from the first half. Also, he bumped up his four-seam usage back over 60% with its increased quality while distributing the rest of his offspeed and breaking balls fairly evenly. Overall, this approach underlies the importance of pitch mix changes. It does not always have to be drastic, but subtle tweaks can make a significant difference. Furthermore, this is the easiest change a pitcher can make in season.
This pitch mix for Nelson proved to be effective at limiting damage, but it is intriguing that his swinging strike rate did not improve. As mentioned previously, his strikeout rate rose to 26.6%, which he has not done before. Generally, that comes with a swinging strike rate of around 14%. This piece by Jon Anderson has a reference table for expected strikeout rate based on swinging strike rate. Also, Nelson had a 15.6% strikeout rate in the first half with essentially the same swinging strike rate. Ultimately, the significant increase in strikeout rate does not feel sustainable. However, he did an effective job of suppressing hard contact and missing the barrel, which is something he had trouble with in the past.
Future Projection
Ryne Nelson finished the 2024 regular season within the top 30 starting pitchers by FIP (minimum 150 innings). While he has provided more confidence that he can be a quality big-league pitcher, it remains difficult to say at this point that he could be a future ace. However, it was an impressive stretch that he went on in the second half. Also, he backed it up with strong peripherals and has always been a Stuff+ darling. Still, he has not been able to convert his Stuff+ marks into swing and miss consistently. That lack of swing and miss limits his ceiling. However, he projects to be an important piece of the Diamondbacks rotation in 2025 and build on his improvements.
Photo Credit: © Troy Taormina-Imagn Images
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