Mound Musings: The Slider – A Classic Love/Hate Relationship

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Published on May 6, 2021

Last week we explored the impact of rhythm on pitching performance. This week, I'd like to dig a bit deeper, specifically focusing on a pitch that is heavily reliant on rhythm – the infamous slider. The three most frequently used pitches, at least among starting pitchers, are the fastball, slider and changeup. A pitcher, in rhythm, and possessing reasonable command of those three pitches has a pretty good chance of success. But, having an exceptional slider could move the pitcher up several tiers in expected performance. That's what makes the slider so popular.

Okay, it can be devastating. So why do I both love and hate the pitch? The love side of the equation is easy. Watching a batter fustily chase a ball out of the zone, thrown by one of your starters for a strikeout is pure joy to a pitching junkie. However, there is a flip side to that coin of joy. First, sliders often create considerable stress on the elbow ligaments and structure – in many cases, the nastier the slider, the higher the risk of serious injury, often resulting in Tommy John surgery. There have been recent advancements in adjusting mechanics to address this problem, but it still exists. And, on the other side of that coin, a poorly thrown slider can be extremely hittable. If it hangs, especially in the middle of the strike zone, it looks like a beach ball on a tee to a major league hitter. The result is ooohs and ahhhs

Breaking down the slider, there are a few things to keep in mind. Regarding the very good ones, a relatively small percentage actually cross the plate in the strike zone, but – and this is absolutely critical – they look like a strike as they leave the pitcher's hand. You have probably heard the term "an easy take" referring to a pitch that never tempts the batter to swing. Since many sliders aren't actually strikes, with no impetus to swing, the hitter simply takes the pitch, putting the pitcher behind in the count, inflating his pitch count (likely shortening his outing), and eventually forcing him to throw a very hittable pitch or risk littering the bases with runners anxious to blow up his WHIP and ERA. A batter misreading the pitch virtually assures a successful outcome.

Next, there are several types of breaking pitches related to sliders – a pitch that can be thrown harder, with sharper, later break, a pitch that isn't thrown quite as hard with more break (a "slurve"), and the other end of the breaking ball spectrum, the curveball, that is thrown even slower with even more break. Our primary focus here will be on a true slider. So, a hitter's take on a good slider will typically go something like this: He first reads the arm slot, which looks the same as that of a fastball. Given the release point, the pitch, assuming it's a fastball, will cross the plate in the strike zone with higher velocity. This deception triggers an incorrect reactive timing mechanism from the batter who attempts to meet the ball while it is in the zone. If it works, the batter will swing too soon at a ball that will dive out of the strike zone at the last second. It works for both same-hand hitters and opposite-hand hitters. The first typically will see the pitch dip to the lower outside edge of the strike zone, or slightly outside of it, while the latter likely will force the batter to dance as the pitch darts toward his back foot in the batter's box. It all sounds easy enough, right?

I'd like to take a look at a couple pitchers who rely very heavily on their sliders, and are currently struggling after the first month of the 2021 season.

Kenta Maeda (Twins, 2-2, 5.34 ERA, 1.57 WHIP): Most pitchers throw fastballs over half of the time, but Maeda is an exception to that pattern. His bread and butter pitches are breaking balls, a slider and a splitter, and both have been somewhat problematic in 2021 for similar reasons. In watching him pitch, it very much appears hitters have adopted a different approach. Rather than looking for a fastball (notably, his velocity is not appreciably different this year) and adjusting to a breaking pitch, they seem to be doing the exact opposite. By taking that approach, the hitters are better able to accurately predict which pitches will end up in the strike zone, meaning they swing at actual strikes rather than swinging at balls outside the strike zone. That means Maeda is behind in the count more often, forcing him to throw pitches in the hitting zone, and batters are enjoying it. Last year, his BABIP was an anemic .208 while it as ballooned to an astronomical .377 this season. There is quite a bit of bad luck in that 2021 number, but it's not all bad luck as more balls are being hit hard. In 2020, Maeda watched a relatively high nine balls sail into the seats in 11 starts. This year he has already allowed seven homeruns in just six starts, and with a lot more runners on base, the damage is greatly multiplied. His pitches, if anticipated, and poorly located, are cannon fodder.

So, Maeda is leaving a higher percentage of his breaking pitches in the strike zone, often up and in the middle of the zone. For example, he typically throws about one-in-five sliders in the strike zone. This season, it's one-in-three. And, with hitters more likely to be sitting on the breaking pitches, they are adjusting to them, being selective and barreling up. The good news is, he has a pitching motion that lends itself to a repeatable delivery. His command can improve. He is a wily veteran, and none of this is a secret to him. I would expect to see a few more fastballs to make it more difficult to sit on the breaking pitches. His strike percentage should increase, meaning he will be behind in the count less frequently, and he should start generating more swinging strikes. His last start against Texas was better. He still missed his spot too often, but it was better. He may not match his incredible 2020 peripherals, but I still expect a solid season.

Patrick Corbin (Nationals, 1-3, 8.10 ERA, 1.76 WHIP): There are quite a few differences between Maeda and Corbin. Maeda is a righty, while Corbin is a southpaw. Maeda has a more varied repertoire, while Corbin offers a bit more velocity, but they both rely very heavily on their sliders. In fact, Corbin is probably more reliant on his than Maeda. As the season began, I wrote this as part of my analysis of Corbin: If he is spotting the fastball on the upper edges of the zone (not an easy take), and his slider is diving down and in to right-handed hitters, typically just off the ground near their back foot, pop a cold one, order a pizza and enjoy the game. If the fastball is easy to lay off, and the slider is arriving knee high or above, you might want to consider munching a handful of antacids and change the channel to a rerun of Field of Dreams. Not a word has changed, and I've seen Field of Dreams a couple times recently.

Corbin does have another challenge to deal with. While the Twins have not played very well defensively, the Nationals, in this age of fundamentally deficient defense, have frequently been awful. That aside, he has to spot his fastball to keep hitters honest, and he hasn't done that consistently. Interestingly, Corbin has experienced extreme ups and downs in his five 2021 starts. In two of those, he has allowed two runs in 13 innings. However, in the other three, he has been blasted for 20 runs in just 10 innings. And, blasted is the appropriate term. Even in the better outings, he has been lucky in some cases as hard hit balls have been right at fielders (and they somewhat surprisingly caught the ball).There has been speculation that his velocity is down a tick. I'll give that one, but the really serious problem is location. Corbin is not consistently locating his fastball or his slider. Most notably, the slider is often crossing the plate well up into the strike zone rather than diving below the zone. I have to admit I am somewhat concerned. This trend dates back into last season, where right-handed hitters batted a robust .321 (they are hitting .319 this season). The solution is a fastball that is close enough to tease right-handed hitters and a slider that makes them dance while swinging weakly. It's been long enough to expect real adjustments. He needs to turn the page very soon.

Some Notable Rotation Ramblings:

The Dodgers have arguably the deepest pitching staff in the game today, but they are experiencing the challenges of multiple injuries. The most recent was fire-balling youngster Dustin May who left his last start with an elbow injury, ending his season, as he will undergo Tommy John surgery.
Royals prospect Daniel Lynch made his major league debut earlier this week, turning in mixed results. He didn't make it through five innings, allowing three runs, but two of those scored after he departed. He did display pretty good stuff, albeit with spotty command, but all in all, it was not bad for a first start.
I watched the Pirates Mitch Keller in his last start against the Padres, and once again I noted his ability to be successful when he trusts his stuff and throws strikes. I'd like to endorse him based on performances like this one, but he has a long history of teasing fantasy team owners (and Pirates fans).
The Rays just keep churning out quality young pitchers, and Shane McClanahan looks like the next on the list. Their top pitching prospect has now made two starts, with impressive results. McClanahan has electric stuff and looks ready for the show, although the team is gradually easing him in with shorter outings.

Endgame Odyssey:

The plan to have Jordan Hicks finishing games for the Cardinals has been put on hold for at least a month. They are being understandably cautious and put him on the injured list, as Alex Reyes continues to get it done in the ninth inning. Joakim Soria is back from the IL, but Arizona may opt to ease him into a high-leverage role. Things have gone reasonably well for Stefan Crichton lately, but I still think Soria's day as their closer is coming. The Twins are underperforming this year, and the back of the bullpen is certainly a major factor. Taylor Rogers took over the closing duties from Alex Colome and promptly started to struggle, but I expect him to shake it off and hold the job. In Cincinnati, the bullpen has also turned into a game of musical chairs. Amir Garrett possesses the best skill set, but he's inconsistent, while Sean Doolittle has experience but has struggled against right-handed hitters. Lucas Sims and Tejay Antone don't look like the answer either. My guess is Garrett will eventually win the job again. The Pirates don't have a lot to sing about this season, but closer Richard Rodriguez has been a true bright spot. He doesn't have prototypical closer stuff, but I am very impressed with his mound presence and focus. The Rays placed closer Diego Castillo on the IL and activated Pete Fairbanks. I like Fairbanks' stuff, and this might provide him with the opportunity to log some saves with Castillo unavailable.