What will Drew Rasmussen look like in 2025?

The Rays, as they are wont to do, boast a surplus of excellent starting pitching — even after trading left-hander Jeffrey Springs earlier in the offseason. But for the oft-injured Rays, perhaps a surplus is never truly a surplus, and sure enough, they added another high-octane arm into the mix last week.

Tampa Bay reached a contract extension with Drew Rasmussen, in which they revealed their intent to re-insert Rasmussen into the starting rotation. That’s a prudent decision, because when healthy, Rasmussen is dominant. He has a career 3.01 FIP, and pitched to a 1.35 FIP with a 10.99 K/9 ratio after returning in August. 

So what might Rasmussen look like in 2025, back in the rotation and with a normal offseason under his belt?

Rasmussen is a natural supinator — self-described as recently as 2023. From a physical standpoint, Rasmussen grips the outside of the baseball upon release. Functionally, that means his mix is defined by gloveside movement. His three main offerings — four-seamer, sinker, cutter — all generate more gloveside movement than league average. In the same vein, supinators have an easier time with strong breaking ball shapes, like sweepers; Rasmussen has one in his pocket, too. 

The cut-off line separating supinators and pronators isn’t exactly clear. Generally, supinators throw four-seamers with a spin efficiency between 60 and 90%; pronators are above 95% efficiency. A few years ago, Driveline’s Chris Langin created a middle ground between the two buckets, for spin efficiencies between 85 and 95%. 

After returning from an internal brace procedure in August, Rasmussen drifted further into the in-between area. I’m curious what that means for his 2025 season, as he transitions back into a full-time starter. What direction should he pursue?

In contrast to supinators, pronators get behind the baseball. That grip lends itself to fastballs with plus armside movement and carry — better shape than their supinator counterparts. On the flipside, pronators have trouble generating extreme horizontal movement; to do so, they need larger velocity gaps between their four-seamers and breaking balls. As a result, pronators often rely on changeups and gyro sliders, essential components of the pronator’s triangle. 

Rasmussen isn’t a pronator — his four-seam spin efficiency has never exceeded 93%. But he’s not quite a classic supinator anymore, either. 

Let’s start with his four-seamer. Last year, Rasmussen threw his FF with 89% spin efficiency and an improved movement profile: compared to 2023, it ran 4.5 additional inches to the armside. It still has more cut action than the average FF, but it’s far less reliant on gloveside movement. In the same vein, he added 2.5 inches of armside run to his sinker, which surged to 90% spin efficiency. 

Curiously enough, this isn’t the first time that Rasmussen has toyed with his FF’s spin efficiency. We can track the various experiments through the table below.

Rasmussen’s FF characteristics, by year	Spin Efficiency	Horizontal Movement	Velocity
2020	93%	6.4 ARM	97.6 mph
2021	90%	4.4 ARM	97.1 mph
2022	83%	2.3 ARM	95.5 mph
2023	83%	0.1 ARM	95.7 mph
2024	89%	4.6 ARM	97.4 mph

The rows highlighted in yellow indicate the years in which Rasmussen pitched exclusively as a starter. These years align with decreased spin efficiency, less horizontal movement, and decreased velocity on his four-seamer. Perhaps that foreshadows what direction Rasmussen takes with his four-seamer in 2025, now that we know he’ll return to the rotation. 

But what might that mean for the rest of his arsenal? Because, over the years, Rasmussen has evolved his mix as his four-seamer took different shapes and efficiencies. 

In 2020 and 2021, when he skewed closest towards pronation, Rasmussen toyed with a changeup, one of the three components of a pronator’s triangle. If his four-seamer sees another bump in spin efficiency, might he try reintegrating a changeup in 2025? It wasn’t a good pitch — Stuff+ gave it a 58, seemingly because it lacked sufficient depth — but perhaps Rasmussen could sprinkle it in against left-handed hitters in a starter’s arsenal. 

Last year, with 89% spin efficiency on his four-seamer, Rasmussen ditched his curveball. He had thrown the pitch 7.3% of the time in 2023 and produced a .160 wOBA, but it’s more of a foundational piece for supinators, who excel at large breaking ball shapes. Can he rekindle its best trait — depth, with six more inches of drop than similar curveballs — despite acting less like a supinator? Or will it be too difficult for him to produce such a depth-y breaking ball? 

And what might happen to his sweeper? It was a tantalizing linchpin for Rasmussen in both 2022 and 2023, limiting hitters — mostly righties — to a .126 wOBA. But pronators are less predisposed to sweepers, and sure enough, Rasmussen’s sweeper became less sweepery last season: 

• 2023: 15% usage // 14.7 in. GLV // 84.5 mph

• 2024: 5.4% usage // 13.6 in. GLV // 85.4 mph

Stuff+ liked the pitch significantly more (115 to 137), but that may have more to do with the velocity bump. And Rasmussen’s velocity ticked up across the board, likely because he could easily empty the tank in short stints out of the bullpen — we’ve seen this before, as shown in the table above. If his velocity diminishes as a starter, will the metrics favor his new sweeper less? 

The velocity gain also aligns with the loss in horizontal movement: Pronators have a greater barrier to entry for significant gloveside movement. To achieve better movement, they need to take something off the pitch. Maybe if Rasmussen takes something off his sweeper, he could recoup some of that horizontal movement. That may be a path forward to sustain his sweeper, if he maintains higher spin efficiency on his four-seamer. If he simply falls back to an 83% spin efficiency, I’d expect his sweeper to more easily gain gloveside movement — irrespective of any velocity changes. 

What version of himself should Rasmussen prioritize, as he acclimates to starting again? Metrics viewed his 2024 alterations favorably, and the results followed. Part of me 

wonders what happens should Rasmussen lose some of his velocity, which I’d expect to happen as he stretches out. Can he succeed as a pronator-lite without elite velocity? I’m not so sure. In the past, Rasmussen has paired faster FFs with higher spin efficiency, and vice versa. And he’s crafted his arsenal with intent to best suit his changing pronator/supinator style. 

So, Rasmussen has two paths. He can continue to boost spin efficiency on his four-seamer, and then lean more on his cutter — a defacto gyro slider — with a changeup and muted sweeper thrown in, too. Or, he can return his four-seamer to pre-injury spin efficiency levels, restoring his sweeper and embracing the cut action on his three fastballs, like he’s done in the past. 

Here’s the fun part: I’m not sure which is best! Rasmussen has succeeded in both ways in the past, and to me, the alterations — contingent on whether he’s starting or relieving — seem purposeful. Perhaps the best answer is a path that puts the least amount of pressure on his surgically-repaired elbow, which wouldn’t be a bad idea. Regardless, Rasmussen should be primed to succeed with either course of action, and I’m looking forward to seeing what his mix and pitch shapes look like come Spring Training.