Will Ryne Nelson Sustain his Excellence in the D-backs' Rotation?

Arizona Diamondbacks' young right-handed starter Ryne Nelson took a massive leap in 2024, becoming one of the D-backs' most consistent arms through the latter half of the season.

After a rough start to his major league career, Nelson seems to have found a rhythm and developed his stuff into a dominant arm.

Now, we'll take a look at his projections for the 2025 season, as part of a series breaking down the individual projections of the 2025 D-backs, including some minor leaguers and non-roster invitees.

These rate projections are a composite of ZiPS and Steamer; the playing time projections are our own, engineered by Diamondbacks On SI's Jack Sommers.

RHP Ryne Nelson, 26

Ryne Nelson statistics and projection | Alex D'Agostino | Diamondbacks On SI

Why Nelson might outperform this projection

Nelson was one of the great success stories of 2024. With the majority of the Diamondbacks' rotation beset by injury or struggling, the young righty quickly became one of the most reliable arms on the staff.

After a slow start, Nelson pitched to a 2.41 and 3.19 monthly ERA in July and August, a crucial facet of the D-backs' success down the stretch.

Nelson has an extremely diverse arsenal, but relied on his fastball 56% of the time in 2024. That fastball was excellent, sitting in the upper 90s for most of the season. While he'd previously struggled to utilize his secondary pitches to put batters away, he began to turn a corner in that regard as the year went on.

Over July and August, Nelson recorded 66 strikeouts over 68.1 innings, after racking up just 46 punchouts over his first 68 innings to open 2024. He was able to record a career-high nine strikeouts in a game three separate times in those waning months.

Of course, especially with such a sudden breakout, there's always a question of whether or not the success is sustainable.

With how poorly Nelson pitched in 2023 and the beginning of 2024, regression is a concern. However, his peripherals suggest that his results were not a facade. His 4.24 ERA (inflated by some early lopsided starts) is backed by a 4.17 xERA, and strengthened by a 3.74 FIP.

That FIP is an excellent indicator that Nelson was not only proficient at preventing home runs, but also at punching out hitters without allowing them to put the ball in play. He was brilliant when it came to throwing strikes and preventing free passes, with just a 5.4% walk rate, 89th percentile in MLB.

As his stuff continues to develop, Nelson could easily smash projections that see him sitting near where he finished in 2024. With regard to these projections, it's important to remember how heavily recent performance is weighted.

Since 2023 and the beginning of 2024 were so poor, his projections will be skewed towards a more pedestrian ERA, but when considering the intensity of his sustained period of dominance to close out 2024, it's not out of the question to see his ERA dip into the 3.00s with an ever-rising strikeout rate.

Much of Nelson's struggles came from sequencing and tunneling his pitches and playing his secondaries off his plus fastball. In the past, his approach left plenty to be desired. But it seems that both his confidence, mound presence and overall approach have taken a huge leap forward. That's encouraging, both for the success of the D-backs, and Nelson's potential to beat his projections.

Why Nelson might underperform these projections

Regression can strike any player at any time. With how dominant and electric Nelson was to close out 2024, it's not unlikely that he'll struggle to get back into as much of a rhythm.

Since much of his issues were clearly strategic or mental, there's a level of uncertainty with regard to its sustainability, even if his raw results were proven to be anything but hollow.

The main issue with Nelson is the reliance on the fastball. While it is certainly an excellent weapon, pitchers who tend to rely heavily on a singular pitch can be figured out.

Now that he's been more exposed MLB hitters, there's a chance they could start to figure him out, and it might take time for the righty to adjust the way he did in 2024. He's no longer a secret weapon, teams will be hunting his fastball and looking for mistakes on his secondaries.

Of course, the other main question is whether or not Nelson will be afforded the opportunity to pitch significant innings. Our projection has him at a mere 110 innings, and with the recent addition of Corbin Burnes, the D-backs' rotation now goes seven deep.

Granted, it will always be better for a club to have more starters. Injuries will almost always happen, as will underperformance. But for now, even if the the D-backs trade Jordan Montgomery, Nelson could find himself in a relief or swing-man role to start 2025.

I wrote about this conundrum in depth earlier this month. The D-backs will have a tough decision to make regardless of whether a Montgomery deal gets done.

Summary

As a whole, it seems more likely that Nelson will surpass these projections than fall short of them. The projection itself isn't anything incredible, and it appears that the young righty has turned enough of a corner to where a poor season for him would be closer to these projections than too far below them.

With an exceptional weapon in his fastball, development in his secondaries and sequencing, and an increasing confidence and ability to perform under pressure, Nelson seems set up to run back his excellent 2024 second half in 2025.

The young righty has shown that he has what it takes, and the peripherals back that up. The question will be whether or not he's given the opportunity to truly realize that potential.