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Red Sox Draft Profile: Kumar Rocker

He has one of the highest ceilings in the draft.

NCAA Baseball: College World Series-Mississippi State v Vanderbilt Steven Branscombe-USA TODAY Sports

We are now under a week to go until we get to this year’s MLB Draft, and the Red Sox are picking as high as they have in a half-century. With the fourth overall selection, the team has a chance to add real, premium talent to their farm system in a way that is just not common for them in their franchise’s history. With that in mind, in the six days leading up to the draft we are going to take a look at what seems to be a near-consensus on the top seven players for the Red Sox to consider with their first pick. We again look at a college pitcher today with a profile on Kumar Rocker.

Baseball America Draft Class Ranking: 5

MLB Pipeline Ranking: 6

FanGraphs Ranking: 8

Kumar Rocker, the son of former NFL defensive lineman Tracy Rocker, has been a highly-touted prospect for a long time. Rocker was one of the top prep arms in the 2018 draft, but his signing bonus demands and strong commitment to Vanderbilt scared teams off. The Colorado Rockies took a flier on him in the 38th round, but he opted to head to college instead, where he quickly made his presence known.

In the 2019 College World Series Super Regionals as a freshman, Rocker tossed a no-hitter against Duke in which he struck out an astonishing 19 Blue Devils. This performance and Vandy’s national title run made Kumar a household name and helped catapult him to the top of many prospect rankings. His 2020 season was obviously cut short due to COVID-19, which brings us to the current 2021 season.

Rocker was the consensus favorite for the number one overall selection at the start of the year, but he’s hit a few road bumps that have lowered his stock. Most worrisome of these has been his velocity fluctuations; Rocker’s fastball velocity typically sits around 94-96 mph, even peaking at 99 mph, but it’s dropped into the low 90’s in a handful of starts this year. A Kumar Rocker who sits 94-96 with his fastball is a very different pitcher than a Kumar Rocker who sits 90-92. The inconsistency with his fastball has led to questions about Rocker’s health and durability.

Despite these reservations, Rocker has still proven himself able to handle a larger workload. He threw 120+ innings this year and produced outstanding results in the process, largely thanks to his exceptional pitch mix and secondary pitches he can rely on. Let’s take a look at what he has in his repertoire.


Setting the aforementioned velocity worries aside, this is a legitimate plus pitch that can cause all kinds of problems for hitters. The pitch features 18 inches of induced vertical break, making it extremely difficult to hit at the top of the zone, and 10 inches of horizontal run, which is very good for a four-seamer. On the flip side, Rocker does not induce a lot of swings and misses with the fastball, instead using it primarily to set up his secondary offerings (more on that later). He also struggles to command the pitch at times, but these are definitely ‘correctable’ issues. If Rocker is consistently hitting the mid-90’s with his fastball, hitters are in trouble.


This is where the fun begins. Rocker is equipped with a nasty plus-plus slider, which also happens to be his best pitch (and one of the best pitches in the draft). It has a very mediocre spin rate of 2200 rpm, but Rocker is able to create a ton of movement on the pitch due to the gyroscopic spin he puts on the ball. The pitch spins on a gyroscopic axis, just like a bullet twirls as it travels, which allows gravity to take over. This results in Rocker’s slider having lots of vertical movement and less horizontal movement (just four inches) than your average slider. To the naked eye, the pitch looks more like a curveball than it does a slider. Check out this filth below.

Rocker also excels at tunneling his slider with his fastball. Circling back to what I mentioned in the fastball section, he frequently uses his fastball to set up his slider. Take a look at his fastball/slider overlay below, and how close to the plate each pitch is before they break off each other’s path.

He gets countless swings and misses with his slider and will throw it at any time in the count. Looks good to me.


The changeup is Rocker’s most underrated pitch. He doesn’t throw it all that often because he doesn’t need to, but it has potential. The pitch features heavy vertical movement and an optimal spin rate relative to his fastball, and he’s able to tunnel his changeup with his fastball in the same way he tunnels his slider with his fastball. Rocker sometimes struggles to locate the pitch, but it can definitely become a plus offering with more reps/usage.


Rocker just added a cutter this year, so there isn’t a ton info about it just yet. It touches high 80’s with a late horizontal break, and he’s mostly used it as a set-up pitch. The cutter’s speed could help his fastball to play up, and its side-to-side movement could pair well with his slider that relies more on vertical movement. That’s about all we know right now.


Rocker hasn’t thrown the curveball much at all recently, instead relying on the 4 pitches listed above. In my opinion, Rocker’s slider renders the pitch mostly unnecessary anyway. However, I thought it prudent to at least bring up the curveball, and mention that people frequently mis-identify his gyro-slider as his curveball.

Talk about a dominant pitch mix. I understand the qualms about Rocker’s fastball velocity and accept that he’s one of the more volatile prospects, but the draft is all about upside, and Rocker has a higher ceiling than anybody. If he can shore up his fastball command and continue improving his changeup, he has legitimate ace potential. Jack Leiter might be the ‘safer’ pick of the two, but Rocker shouldn’t fall out of the top 5.