2021 MLB Draft Scouting Report: Kumar Rocker

It’s July. The sun is shining. Baseball is being played. The Seattle Mariners are in prime position to select middle linebacker right-handed bulldozer Kumar Rocker with the first pick in the 2021 draft.

This kid is an absolute unit.

Rocker was actually a 38th round selection by the Colorado Rockies in 2018, but didn’t put ink to paper due to sign-ability concerns. Most evaluators had Rocker being a first round talent in that draft.

As of today, Rocker is the odds-on favorite to go first overall. After an eye-popping freshman campaign in 2019, his stock had never been higher. Rocker was nearly an unanimous Freshman College Baseball Player of the Year by just about every publication. He took home the College World Series ‘Most Outstanding Player’ award, and threw a no-hitter in said World Series. He pitched nearly 100 innings, striking out 114 and walking just 21 along the way.

It was, by almost any measure, a historic freshman campaign.

His 2020 sophomore season was obviously quite abbreviated, as Rocker logged just 15 innings before the shutdown. Those innings did not disappoint. 28 punch outs and a 1.80 ERA suggest he was headed toward a massive showing.

Still, as good as the numbers have been in the box scores, it’s important to explain how exactly Rocker gets batters out. After all, big league organizations draft for stuff and projection, not the ability to embarrass 19-year-olds from the University of Illinois-Chicago.

I’d be remiss not to talk about the mechanics of his delivery and potential for longterm durability. Rocker has largely been a healthy player at every state. He was lightly hampered by a slight hamstring strain in high school, and dealt with some very general, non-acute arm soreness for about a week in 2020. His delivery is nothing to be alarmed by.

Rocker’s delivery is very athletic, especially for a bruiser of his size. It’s remarkably balanced and repeatable featuring a clean, quick motion that effortlessly works through long appearances. Rocker’s release point is also impressive and repetitive. On multiple occasions, Rocker surpassed the 110-pitch threshold, highlighted by a 131-pitch performance in his no-hitter against Duke.

TOOLS (Future Value)

Fastball: 60

It all starts with the fastball. Rocker’s heater is impressive, there’s no doubt about it. The velocity comfortably sits 95 on any given night and touched as high as 97 this season. He’s been clocked as high as 99 going back to his days North Oconee High School in Georgia, and as recent as his freshman campaign in Nashville. There’s some familiarity between Rocker and some Mariners too. With all due respect to the potential big league ace, Jarred Kelenic owns him.

It’s not just the mid-to-high 90s velo that draws rave reviews for Rocker’s fastball. The heater just explodes at the plate. The 18.2 inches of induced vertical break (ride) is certainly plus and can be un-hittable at the top of the zone. Not to be outdone, the 10 inches of horizontal run on the pitch is really, really good for a four-seam fastball. The near 7 feet of extension he gets on the pitch is good as well, especially for a 255-pound workhorse. What does all this mean? The pitch can be an absolute nightmare on right-handed hitters when it’s spotted up, and especially inside. It’s legitimately terrifying. It’s gotten him in some trouble at times.

In fact, during the 2019 College World Series, the no-hitter that he tossed against Duke would have been a perfect game had he not walked a couple batters and allowed a fastball to get away from him and hit a Blue Devil in the face. Still, he’d go on to strike out 19 batters.

The fastball, at its worst, is above average with the very real potential, and I’d even go as far as to say likelihood, of being a plus, maybe even 70-grade offering at the next level. It boils down to whether Rocker will be able to not only control the heater at the big league level, but also command it to his spots. He’s struggled with that thus far.

Slider: 70

All that being said, the fastball might legitimately be his second-best offering. The slider is already a clear-and-present 70-grade offering and he commands it better than his fastball.

The slider has some of the same tendencies of Nationals ace Max Scherzer’s. Some sliders have horizontal movement, breaking across the zone from a pitcher’s hand. Other sliders, like Rocker’s, produce exceptional vertical movement with little side-to-side tilt. Rocker gets just 4 inches of horizontal sweep.

This is due to gyroscopic spin. This is achieved by spinning the ball out of a pitcher’s hand like a bullet twirls as it travels. It spins on a gyroscopic axis allowing gravity to do all the work.

Basically, the pitch falls right the table toward the dirt due to the nature of its spin. Conventional breaking balls spin on a transverse axis. Gyro spin is less affected by air density and resistance. The only reason this isn’t classified as a curveball (as the eye would perceive it), is because the spin axis is totally opposite. Curveballs tumble end-over-end... gyroscopic sliders spin in the same way a football does. These pitches to Duke hitters are exactly that: a vertical-breaking, gyroscopic slider.

His slider only averages roughly 2250 RPMs, so the gyro-spin is important as he won’t be able to exceptionally sweep a breaking ball with this kind of spin. When the gyro spin is as pronounced as it is here, less spin actually works in Rocker’s advantage. The pitch still barrels to the plate at 85-86, touching 88 in 2020. That’ll play.

As mentioned before, Rocker has a better feel for his slider than he does his fastball at this stage. So long as the pitch doesn’t regress and maintains its spin characteristics, it’s big league ready. Right now. Plain and simple. It’s filthy.

Changeup: 55

Now, let’s discuss the changeup, because many evaluators, including myself, believe it has the potential to become a consistent plus offering in the future. Right now, it isn’t deployed often because, well, it simply doesn’t have to be. Rocker works almost exclusively fastball-slider at Vanderbilt because he hasn’t had a need to veer off that course.

The changeup’s biggest wart is the command and consistency. The pitch shape is great. The 17.1 inches of horizontal run on the pitch mirrors the fastball quite well, and he couples that with decent vertical depth. 1700 RPMs on a changeup is very good. You want that to be low, and it is. Like most pitches in his arsenal, Rocker gets ideal extension for his changeup at 7 feet.

Frankly, the characteristics of Rocker’s changeup are similar to that of Steven Strasburg’s changeup. The issue right now is repeating the offering and spotting in on the black or below. When put low-and-inside to right-handed hitters it plays off the slider really nicely. If he can reach a point where he throws it consistently, it has the qualities of an above average offering, maybe better.

Rocker has thrown a traditional curveball in the past, but in general, works off the three pitches above. He may develop a curveball between now and his big league debut, but for the time being, it’s probably not worth mentioning.

Final Thoughts

The book on Rocker is reasonably simple. Fastball command will ultimately dictate whether he has a mid-rotation ceiling or a true ace. He’s yet to be a guy that issues a lot of free passes, but big league ball would likely exacerbate fastball command concerns. Despite his size and accomplishments, he’s still entirely projectable with inefficiencies in fastball command and spin efficiency. There’s a lot to like in Rocker including his demeanor and competitive arsenal. He’s a premier talent and likely will not last past the Top 3.

That being said, whenever you’re talking about a 18-19 year old who’s already pushing two and a half bills, there’s pause. Rocker is built like a house, and it’s a pretty strong, sturdy body. He may run into some issues toward the latter half of his big league career, but for the time being, the body isn’t much of a concern.

Seattle got very lucky in seeing Emerson Hancock, the presumptive number one pick a year prior to the 2020 draft, fall to them at 6. It’s unlikely Rocker would have a similar fall save an unexpected injury.

All signs, whether you like it or not, point toward a top five selection in the 2021 draft for the Mariners. Whether it’s “FUBAR for KUMAR” of “Hit Rocker Bottom”, there are silver linings in rooting for an underperforming team.