Best Curveballs Among 2023 Top 100 Prospects
Where have all the curveballs gone? What was once a standard part of any pitcher’s arsenal has gone by the wayside, often maligned in analytical circles and hardly thrown at the rate of sliders or changeups. This begs the question: Is the curveball going extinct?
The answer bluntly is no. The reality is more and more pitches that were once branded as curveballs are now branded as sliders. While the slow, heavy-breaking curveball isn’t as prevalent as it used to be, it can still be an important pitch for many pitchers' success. Below we’ll discuss a handful of curveballs thrown by Top 100 Prospects that are not only effective pitches but important elements of their arsenals. These are the best hammers in the Top 100 Prospects.
Key Curveball Metrics
Velocity: This one is simple—the harder you throw the better.
Induced Vertical Break (IVB): This is a metric used by ball flight-capturing devices (For example: Trackman) to determine how much a baseball moves up or down from a central point of zero. We looked at IVB on fastballs to see how much ride or hop the fastball generates. With curveballs we’re looking at the opposite—how much depth or drop does a curveball generate? While four-seam fastballs use back spin, curveballs use top spin, meaning their spin induced movement makes the ball curve or drop down.
Horizontal Break: Simply how much the pitch moves horizontally. When discussing sliders all horizontal break is toward the pitchers glove side. A combination of IVB and horizontal break is common among the best curveballs.
Whiff Rate: The rate of total swings against a pitch that results in a swinging strike or a whiff. This is the purest way to determine how well a given pitch misses bats.
Chase Rate: The rate of total swings against a pitch that induces chases or swings out of the zone.
Called + Swinging Strikes Rate (CSW%): The number of called strikes and swinging strikes added together and then divided by the total number of pitches.
Weighted On Base Average (wOBA): Weighted On Base Average is a variation of on-base percentage that weighs each method of getting on base differently. Think of it like this; a walk is worth less than a double and a double is worth less than a home run. This is an excellent way to view a pitcher’s ability to drive outs.
Expected Weighted On Base On Contact xwOBAcon: xwOBAcon is useful when analyzing fastballs for a very simple reason. It eliminates strikeouts and walks and only measures the quality of balls in play. It also excludes foul balls unless they result in an out, which is a useful inclusion when looking at fastball quality. The ability to induce infield fly balls and foul pop outs is a skill and is a common characteristic of pitchers with high induced vertical break and a flatter fastball plane. While more complex in its construction, xwOBAcon allows us to remove things we can measure with other metrics (Ex: whiffs or called strikes, etc.) and isolate the quality of contact against the pitch.
Exclusions: As we did in the best fastball and slider articles, we will exclude the Guardians' Daniel Espino and the Rays' Shane Baz due to a smaller sample size not in line with the rest of the group. We’ll also eliminate both the Mets' Kodai Senga and the Padres' Dylan Lesko as neither has thrown a pitch in front of a ball-tracking device in North American affiliated baseball.
1) Cade Cavalli, RHP, Nationals
Velocity: 86 mph | BA Stuff+ 124 | Whiff%: 42%
After a rough stretch to begin the 2022 season, Cavalli figured something out in late May, and it catapulted the rest of his season forward. Over his first seven starts Cavalli was the owner of a 7.62 ERA. The next 13 starts were a much different story, as Cavalli allowed just 16 earned runs over his next 68.2 innings. So what changed? Why did Cavalli transform into a better pitcher?
His curveball. Cavalli began to throw his double-plus curveball more than twice as much following his first seven starts. Over that period, Cavalli’s curveball usage was just under 17%. Over the final 13 starts in Triple-A that number jumped to just under 25%. Why was it such an effective pitch?
Cavalli’s combination of power and movement allow his curveball to dominate opposing batters. Over a sample of nearly 400 curveballs, Cavalli generated whiffs at a rate of 42% while inducing ground balls against the pitch at a rate greater than 75% during that time. A curveball at 85 mph with over -10 inches of induced vertical break is a true hammer curveball. Cavalli throws far and away the best curveball in the Top 100, and in truth it might be one of the best curveballs at any level of baseball.
2) Hunter Brown, RHP, Astros
Velocity: 82 mph | BA Stuff+ 107 | Whiff%: 30%
Few pitchers have the power across their arsenal quite like Brown. The Astros righthander has one of the fastest four-seam fastballs and sliders in the Top 100. He has two contenders for his best pitch between his upper-90s four-seam fastball and hammer curveball. Armed with a four-pitch mix, Brown’s curveball saw the highest usage of his three secondaries, just edging out his low-90s slider.
What makes Brown's curveball so good? Like Cavalli, it’s a combination of unusual power and significant depth or drop. Brown’s curveball had an average velocity of 82 mph, while averaging over -15 inches of IVB or drop. This combination of power and depth makes it hard for hitters to barrel.
Over a sample of nearly 500 pitches, Brown generated whiffs at a rate of 30% while inducing ground balls over 65% of the time against the pitch. This combination of outcomes against the curveball led to the fourth-lowest wOBA by opposing batters on the Top 100, as hitters produced a weighted on-base average of .200 against the pitch. Brown uses the curveball heavily against lefthanded hitters instead of a changeup.
3) Matthew Liberatore, LHP, Cardinals
Velocity: 74 mph | BA Stuff+ 96 | Whiff%: 38%
Things haven’t gone as planned for Liberatore over the past two seasons. Following the Covid-19 pandemic Liberatore was aggressively assigned to Triple-A Memphis at 21 with no previous professional experience above High-A. He made 22 appearances for Triple-A Memphis in 2021, producing a solid but unspectacular line. In 2022 he returned to the level, making 22 starts for Memphis and shuttling between the big leagues and Triple-A.
What’s often lost on the general collective is how hard it is to pitch in Triple-A and how few starters have success at the level. Liberatore was one of the youngest pitchers at the level in consecutive seasons. This led to many ignoring what Liberatore did well, which was his innate ability to spin the baseball and throw five different pitch types in any given start. While Liberatore’s slider has performed well, it’s his slow, mid-70s breaking ball that is the lefthander’s most effective pitch.
Sitting 74-76 mph, Liberatore’s curveball is far more traditional in shape and speed than Cade Cavalli’s or Brown’s. Despite the lack of power it’s a very effective bat-misser, as Liberatore’s 38% whiff rate against the pitch is the third-highest whiff rate on any curveball thrown by a Top 100 pitcher. Part of the reason for this success is Liberatore’s ability to generate heavy depth, as the pitch averages over -16 inches of induced vertical break. This ability to change a hitter's eye level led to above-average whiff rates, and like many heavy-breaking curveballs, a high rate of ground balls induced against it. Liberatore’s combination of depth, location and high raw spin rates in the 2,700-2,800 range make his curveball one of the best in the minor leagues.
4) Tanner Bibee, RHP, Guardians
Velocity: 78 mph | BA Stuff+ 93 | Whiff%: 34%
Few pitchers came out of nowhere quite like Bibee. After a college career that billed Bibee as a command-over-stuff guy, he emerged early in 2022 with significantly upgraded power across his arsenal. Bibee added not only velocity to his fastball but to all of his secondaries. Bibee’s slider, changeup and curveball all became viable pitches he could throw in any count to any handedness.
Bibee’s curveball might be his third- or fourth-best pitch truthfully, but despite this, it’s arguably one of the most important pitches in his arsenal. Why? Simply put, Bibee’s curveball shows less platoon splits than his changeup and slider. Against lefthanded hitters, Bibee’s curveball acts as his primary breaking ball. It generates a high rate of ground balls against lefthanders while inducing whiffs at a rate above 30%.
Against same handed batters, Bibee uses it as his third pitch, showing a different look off of his primary mix of fastball and slider against righties. The pitch behaves differently in these matchups as well, as the curveball generates a much higher rate of whiffs against righthanded hitters. In fact, Bibee’s in-zone whiff rate against righthanded batters with his curveball is nearly 40%, the highest number of any curveball on the Top 100. It is a formidable offering that acts like the glue of Bibee’s supercharged pitch mix.
5) Gavin Williams, RHP, Guardians
Velocity: 77 mph | BA Stuff+ 88 | Whiff%: 41%
Already armed with the best fastball among the Top 100 Prospects, how many more awards does Williams need? Possibly a few, as Williams, like D.L. Hall and Bobby Miller, has one of the best pitch mixes of any pitcher in the minors. While Williams' primary one-two punch is his mid-to-upper-90s four-seam fastball and his mid-80s slider, his mid-to-high-70s curveball is an essential part of his pitch mix and sequencing.
While Williams' curveball surprisingly lacks power, its depth is greater than any curveball thrown by a Top 100 prospect—it averages over -18 inches of induced vertical break or drop. With a high-ride fastball attacking the top of the zone at 95-99 mph, it’s almost unfair that Williams can drop his velocity by 20 mph with a nearly opposite movement profile from his four-seamer. This ability to drastically change eye levels drive whiffs against the pitch, as Williams' whiff rate of 41% was second only to Cade Cavalli among Top 100 Prospects.
His curveball isn’t just a whiff inducer, either, as his 74% groundball rate against the pitch also rivals Cavalli’s. The pitch acts as his primary secondary against lefties, and the results speak for themselves. Lefthanders hit just .160/.276/.160 against the curveball with an 83% groundball rate and a 41% whiff rate. While Williams' slider and fastball might grade out higher, his curveball is a true weapon in offhanded matchups.