A Breakout Lefty Has Emerged. What's Up with Kumar Rocker?

Ryan Weathers, Kumar Rocker, More New Pitches

Ryan Weathers, LHP, Miami Marlins

Weathers’ shape and velocity data from spring training are nutty. His fastball sat 98 mph, topped out at 99 and maintained 19”+ vertical break and 11” arm-side run from a 5.9’ release with 6’ extension. Last season, he sat 96 mph with 15” vertical break and 12” arm-side movement from a 5.8’ release. Overhaul is an understatement. The comps on this shape are something better than Cole Ragans, Garrett Crochet and MacKenzie Gore, all are either lacking the vertical break or velocity that Weathers is flashing. Sure, it’s spring training. It’s two innings. Stuff+ hasn’t even stabilized yet. But even if Weathers gives back some of these gains, there’s a strong chance he’s something like 97 mph with 18” vertical break, which would give him one of the best left-handed fastballs in MLB.

What jumps out most on his plot is the separation between his fastball and changeup. Even with the increase in vertical break on his fastball, he has pushed the vertical break on his changeup lower, creating even more drop on the pitch. It averaged 0” vertical break with 13” arm-side movement at 87 mph yesterday compared to 2” vertical break with the same arm-side late last year at 87 mph. That’s ~19” of induced vertical break separation between his fastball and changeup. The average difference between four-seam and changeup vertical break last season was 9” for left-handed pitchers, with arms like Carlos Rodon and Joe Mantiply touching 14” of separation. Weathers has almost doubled the average differential.

But wait, there’s more! Weathers added a gyro slider, a pitch he lightly flashed last year. This iteration routinely has 3”+ glove-side movement at 90 mph compared to his small-sample version last year, which sat in the 0-1” area. His sweeper touched 18” sweep and sat around 16” sweep, a 2” gain from last season while holding velocity at 84 mph.

As public analysts, we sometimes get carried away with saying simple things like, “This pitch should have more vertical break and this changeup should have more drop.” We’re mentally trained on stuff models, which encourage big shapes. The implementation of our brash suggestions is far more difficult. But in the case of Weathers, the Marlins played pitch design and everything stuck in a game situation.

I’d love another sample of 30-40 pitches to verify the adjustments, but you have to act quick on flag-planting like this before the masses get to the information. If you’re looking for the next lefty to pop, like Garrett Crochet last year or Cole Ragans in late 2023, Weathers is the leading candidate. Stuff+ is going to fall in love.

Kumar Rocker, RHP, Texas Rangers

If 2 innings are enough for me to buy into Ryan Weathers, they are also enough for me to scratch my head at why Rocker abandoned his signature slider in his February 25th spring outing. Rocker’s curveball—a pitch he threw just 2 times last year—acted as his primary breaker. I’m fine with the concept of more curveball if it’s in early count situations. The shape isn’t good enough to work outside of those spots. 79 mph with -10” vertical break and 6” glove-side is a below-average shape. My main concern is why he wouldn’t throw his best pitch from the jump in spring? It’s an offering that had me wondering if it was one of the best sliders in baseball the second he stepped on an MLB mound. And it was nowhere to be found last Tuesday. He did flash what looks like a new cutter, but it was one pitch and was at a notably higher velocity band to assume it was an overthrown slider.

I’ve heard some organizations encourage curveball usage early in careers before adding harder sliders as a way to stimulate more supinated positions at release. I also had individuals in other organizations groan with skepticism when presented with this strategy as beneficial for pitchers. Perhaps Rocker is attempting to use the curveball to bridge the feel to his slider and it’s just a matter of time before he adds it back? I’m happy to give him the benefit and assume that’s the case. But even if that’s the case, my concern becomes when he threw the pitch last. If the answer is further in the distance than, “in one of my latest bullpens,” are we confident his feel for that pitch exists as strongly as it did last season? A season where Rangers organization saw the fruits of their labor reworking his delivery to catalyze his success.

I expect Rocker to pitch again Tuesday. We’ll see if he throws his slider. Maybe I’m overreacting, but it seems odd to not throw your best pitch from square one.

Quick Hits

Since my last “ultimate new pitches list” post, more have emerged…

-David Festa (MIN) - sinker

-Will Warren (NYY) - curveball

-Nathan Eovaldi (TEX) - sinker

-Andres Munoz (SEA) - kick-changeup

-Jack Leiter (TEX) - kick-changeup

-Bobby Miller (LAD) - sweeper

-Brady Singer (CIN) - cutter

-Kris Bubic (KCR) - cutter

-Robbie Ray (SFG) - changeup

-Gavin Williams (CLE) - slider tweak

-Grant Holmes (ATL) - kick-changeup

-Brandon Sproat (NYM) - sinker