Underthrown Pitches And The Pitchers Who Underthrow Them

Identifying pitching breakouts as they happen can be hard. Anticipating them, even harder. Savvy readers of sites such as this rely on plate discipline metrics, batted ball data, and other indicators designed to tease out luck from results in order to uncover which performances have staying power and which are fleeting. And while we’ve arrived at the point in the season when most pitching rates have stabilized, a simple change in pitch mix can render those indicators obsolete. Think Matt Shoemaker and his splitter, Jake Arrieta and his cutter, Max Scherzer and his curveball, or Sonny Gray and his slider.

If you can spot a pitcher pulling unexpected arrows from his quiver as he does it, then cheers to you. But it’s difficult to do that at scale. While trying to anticipate a change in pitch mix before it happens may seem futile at times, doing so is a bet on potential. And what we talk about when we talk about “stuff,” is really potential. One of the components upon which that potential relies, aside from command and health, is an optimal pitch mix.

To identify which pitchers could benefit by throwing their more effective offerings a little more frequently, we have a number of tools at our disposal. Today, we’ll use some of those tools to identify the league’s underthrown four-seam fast balls and sinkers and the pitchers who underthrow them.

First, an explanation of the methodology and one important caveat. I pulled starting pitcher data from Baseball Prospectus’ Pitchf/x leaderboards for all starters meeting the following qualifying minimums:

Within the seven pitch types, I graded each starter’s offering based on three criteria: whiffs, ground balls, and pop-ups using two metrics, whiffs per swing and ground ball-plus-pop up rate per ball-in-play. I then converted those metrics into Z-Scores and summed them to arrive at a final Pitch Score. And yes, the Pitch Score could be improved by incorporating a measure of control, such as called strike-to-ball ratio or Zone-percentage but that gets tricky on out-pitches or those purposely thrown off the plate; think a spiked curve or anything Dallas Keuchel throws.

To identify which pitches might be underthrown, I used a simple measure of effectiveness-to-frequency, or Pitch Score divided by the percentage a specific pitch is thrown. Let’s call it the Underthrown Index, or UI. For example, according to UI, the most underthrown changeup belongs to Tyler Chatwood, whose changeup’s Pitch Score ranks as the highest in baseball based on whiffs, ground balls, and pop-ups; however, he only throws the pitch 7% of the time. That combination of a highly effective pitch thrown with relative scarcity makes Chatwood’s changeup one of the most underthrown in the game.

UI is not a perfect metric in part because the more infrequently a pitch is thrown (i.e. the smaller the denominator) the larger the UI; in essence it gives priority to small sample sizes. However, having set the threshold at 200 for fastballs and 50 for secondary pitches, we mitigate some of that sample size risk.

Now, analyzing pitches in isolation (i.e. as not part of a larger arsenal) can be misleading. Chatwood’s changeup, or anyone’s for that matter, really only exists in the context of a fastball. Throwing the change too often at the expense of his cheddar negates some of its effectiveness. So when I suggest that Chatwood throw his changeup more often because it appears to be a good pitch, there’s obviously a point at which throwing it too often results in diminishing returns. The point of this analysis isn’t to establish the ideal frequency, though admittedly that’d be awesome. Rather I’m attempting to identify which pitchers may be just a tweak or two away from a more effective mix and perhaps a breakout.

Four-seam Fastballs

Adam Wainwright claims the most underthrown four-seam fastball in baseball. Its ranks 84^th out of 102 pitchers in rise, 88^th in velocity, and 98^th in horizontal movement. It’s slow and straight and hittable, as evidenced by his 12.5% whiff per swing rate, good for 91^st among starters. That he tops this leaderboard is what you might consider an odd result. Given however that Wainwright is actually throwing his heater more often than he has at any point in his career, I doubt its effectiveness is as surprising to him as it seems to us.

Wainwright can attribute that effectiveness to some masterful contact management. His four-seamer induces ground balls 71% of the time. That’s 12 percentage points higher than the next guy, over 3.5 standard deviations better than the mean, and most remarkably, 30% higher than his personal career average. There are only 19 other individual pitches in baseball that generate a higher ground ball rate than Waino’s four-seamer; many of those are sinkers, curves, and changes specifically designed to do just that. Going back to 2007, the earliest we have such data, the closest comp is Samuel Deduno, whose four-seamer induced grounders on 68% of balls-in-play in 2012. In other words, Adam Wainwright currently owns the most worm-burningest four-seamer to ever burn worms in the Pitchf/x era.

So what is Wainwright doing differently this year? Looking at his heat maps, it appears he’s challenging lefties down-and-away when historically, he’s been out over the plate against them. Sure enough, locating down-and-away has induced a ton of ground balls. He’s also challenging righties in on the hands, generating similarly elevated four-seam ground ball rates to like-handed batters. Who’d have thought that hitters would have a harder time squaring up balls on the edges of the plate rather than over the heart of it?

To both righties and lefties, Wainwright has become more discerning with his fastball location, which is undeniably a positive development. But does that mean he should throw the pitch more often? Well, given its league leading .000 isolated slugging percentage, I’m inclined to say yes, as long as he continues to locate as stringently as he has been.

It’s now been four years since Wainwright last struck out batters at a better than league average rate. Despite questionable defense behind him, his pinpoint fastball command has seemingly created a powerful ground ball weapon that he’s leaning on more heavily this season. And after having served up the cheddar 31% of the time in a recent start in Colorado, I’m looking forward to seeing the Pitchf/x data from yesterday’s start against the Dodgers.

Other pitchers underthrowing their four-seamers include:

Jacob DeGrom: by whiffs, grounders, and pop-ups, DeGrom has had the best four-seamer in baseball this year. He’s throwing it about 43% of the time, which is league average, so while he could definitely throw it more often, it’s difficult to foresee an extreme surge in frequency. But with a 39% whiff per swing rate, DeGrom’s four-seamer is as whiffy as Wainwright’s is heavy.

Carlos Martinez: throwing his 97 mph four-seamer just 29% of the time, Martinez could certainly throw it more often. However, his pitch mix is extremely well-distributed which may in part elucidate the overall effectiveness of his arsenal. Martinez excels across all three criteria. His four-seam whiffs per swing rate ranks 24^th out of 102 pitchers, his ground ball per ball-in-play 35^th, and his pop up rate 16^th, combining to give him the 8^th most effective four-seam fastball among starters.

Kyle Hendricks: after a rough three-start stretch to open the season, Hendriks appears to have righted the ship. While doing so, he’s leaned more heavily on his four-seamer. While poor at generating swings and misses, the pitch has induced a grounder or pop-up in 55% of balls-in-play, the 10^th highest frequency in the league among four-seam fastballs.

Sinkers

To read Brooks Baseball’s estimation of Matt Harvey’s sinker, one would understand why he throws it so infrequently:

His sinker is an extreme flyball pitch compared to other pitchers’ sinkers, has less armside run than typical, has little sinking action compared to a true sinker and has slightly above average velo.

Extreme fly ball? Not this year. Yes, its 71% ground ball per ball-in-play merely matches that of Wainwright’s fastball but among the league’s other sinkers, it ranks 8^th. It’s as if he traded in those fly balls for grounders yet still found a way to keep the pop-ups, a measure by which the pitch also ranks 8^th, by the way. Now, at 10.71% whiffs per swing, it doesn’t induce many misses but maybe that’s not so bad.

Harvey’s sinker has garnered a .083 isolated slugging against, which ranks 23^rd out of 126 pitchers. And his .333 slugging against ranks 19^th.  It helps that Harvey appears to burying the pitch low and away, often off the plate. It also helps that despite living on the fringes of the zone, it has one of the league’s better called strike-to-ball ratios. And that combination of un-barrelable location and almost perfect proximity to the strike zone, makes the pitch extremely difficult to do anything with.

At 7.7%, Harvey is throwing his sinker more than at any point in his career. While it’s not a sexy out-pitch, using it more often to steal called strikes could indirectly lead to more punch outs. And when hitters do make contact, it’s also a difficult offering to elevate.

Despite going to the well 31% of the time, Brandon Finnegan may also stand to benefit by throwing it more. It’s that good. Its Pitch Score is twice that of the next sinker on the list and it’s elite both in terms of whiffs and grounders, ranking first in both categories.

The average sinker-baller throws the pitch a little under 30% of the time so Finnegan is more or less average in his usage. But leaning on it more heavily at the expense of say, his slider, could do wonders. Then again, why only throw his sinker more? While he’s fallen short of the qualifying four-seamer and changeup thresholds due to injury, both have been excellent to elite this year. Brandon Finnegan, please come back soon.

A complete list of the underthrown four-seamers and sinkers can be found below. I pulled the data on Tuesday morning, 5/29, so it doesn’t reflect any start since then.

Next week, we’ll check out the league’s underthrown cutters and curves.