Eric Jagers Talks Pitching

Eric Jagers is on the fast track in the pitching world. Little more than seven years after discovering Driveline during his freshman year of college, the 25-year-old Iowa native is now the assistant pitching coach for the Reds. Promoted to the position last month — he replaced Caleb Cotham, who is now the Phillies’ new pitching coach— Jagers spent last season as the club’s assistant pitching coordinator. Previously Driveline’s Manager of Technical Development, he remains with the Seattle-area training facility in an advisory role.

Jagers touched on a handful of pitching-related topics, and a pair of Cincinnati hurlers, earlier this week.


David Laurila: What do many people not really understand about the technological aspects of pitching development?

Eric Jagers: “That’s a good question. With all the pitch-tracking technology — and there are a lot of people who do understand this — it’s all the pieces together, as opposed to the segmented ways we tend to look at things: a pitch has got this movement, and it’s also got this location. But really, those things morph together. The location piece adds to the movement piece. A fastball with a lot of hop that’s also up in the zone is maximized. Same with a sinker that’s at the bottom of the zone. Conversely, with a sinker at the top — when we’re looking at short-form movement — it’s easy for the data to fool you into thinking it’s something it’s not.

“I think a lot of people are pretty comfortable viewing movement on TrackMan, Rapsodo, and now Hawk-Eye. But those are just giving us a piece of the equation. We need to factor in all the variables.”

Laurila: Can you elaborate on what you mean by data fooling you into thinking it’s something it’s not?

Jagers: “It’s easy to come up with an answer, and the easiest person to fool is yourself. It’s like the Richard Feynman quote. Basically, it makes it really easy for us to tell us the story that we want to tell, and we don’t have a full understanding — at least on surface-level stats — of what a complete pitch is. Going back to location and movement, in order to get a true vertical-break number, it’s not just 18 inches of spin-induced vertical movement. It’s that, plus where it was released from, plus where it entered the zone. All of those things together equate to one true number.

“The idea itself is old. People like Mike Fast, and the crew at Baseball Prospectus, back in the day, were way ahead of their time. A lot of people now are talking about vertical approach angle. Going back to my example, the number is highly dependent on where the ball is located, as well as where it’s released from. Using the end location as the result, say I throw one at the very top of the zone, and one at the very bottom. Okay, the average tells us that it would be right in the middle. But it’s neither of those two truths. It’s sort of lie. It’s a data point that can be misleading.”

Laurila: Amir Garrett’s slider has an interesting profile. How would you describe it?

Jagers: “It doesn’t jump out metrically — at least not when we’re talking about things like break and spin rate — but it certainly performs well. He puts it in the right places, and he’s certainly convicted in the pitch.”

Laurila: What makes it so effective?

Jagers: “It’s generally firm, and he commands it well, so there are some factors at play there. But Amir is definitely interesting from the Hawk-Eye/TrackMan perspective. There may be some things that TrackMan wasn’t telling us, and there are some things we’re starting to learn from Hawk-Eye data.

“With the capabilities of Hawk-Eye, it’s ‘Okay, it was a swing-and-miss, but what’s inside that swing-and-miss? Where was the miss?’ We’ll be able to track things like the magnitude of the miss from the bat. Was it four inches down and to the right, or is he more missing bats down and to the left? Or straight down? Different profiles will tell you a different story. That said, we don’t actually do this — not yet — but it’s something I hope we’ll be able to measure in the near future.”

Laurila: Sequencing would come into play there, and also deception.

Jagers: “Right. Deception is one thing that people are pretty quick to jump to with Amir: he’s left-handed, it’s funky. There’s no doubt about that. There’s certainly an art that you have to appreciate, but you want to understand it as well.”

Laurila: I’ve always been intrigued by how backup sliders are often effective.

Jagers: “You’re playing the the draw, if you will, with that pitch. You’re playing the slide or the sweep, and when it doesn’t do that, it hits you with a little bit of a surprise attack. In some respects it’s a good pitch because it was a mistake.”

Laurila: My assumption has been that hitters are recognizing slider spin and thus reacting to movement that isn’t there. But is that actually happening? Are hitters actually reading the spin?

Jagers: “First, I don’t know. Second, I do think there is probably something to be said about velocity and sequencing. A hitter may not actually be reading the spin, but rather anticipating it.”

Laurila: Earlier you brought up where the ball is released from. If Amir Garrett had a different release point, would his slider maybe be less effective?

Jagers: “I don’t necessarily know if that would be true. I do think you could view it as just another variable in the equation. You’re changing something about the trajectory of the ball, but if we hold all of those constants… I think that people are just identifying outliers, outside of just surface-level spin rate, from those sort of characteristics.”

Laurila: Changing direction, you spent a lot of time at the team’s alternate site this past summer. Who stood out there?

Jagers: “One guy that was really exciting is José De León. He didn’t have the most incredible showing [in Cincinnati], but if you look at the quality of his stuff, there are a lot of things that jump off the page. We’re talking four miles per hour on the fastball. I remember watching a game — it was maybe his second or third outing in the big leagues — and seeing 97 on the radar gun. I think that was the best of his career, and it was’t just one pitch; it was something like four pitches in a row.

“There’s also his slider. He had 13-and-a-half inches of horizontal break in 2020, which was up from four inches in 2019. The spin rate jumped up by 400 RPMs.”

Laurila: I assume the velocity went up as well…

Jagers: “It did, but only by 0.7 [mph]. By throwing the ball better and devising a more optimal grip for breaking balls, you can spin it higher. You can spin the ball better without substances; you can spin the ball better by simply ripping it better.”

Laurila: How did De León go about making that improvement?

Jagers: “He had toyed around with sort of a slurve-style pitch, but had also thrown this harder bullet-style slider in 2019. The idea was to morph those together and create a sort of middle ground. Basically, he was able to leverage the outside of the ball and create more side spin than what he previously had. That was done by walking back the slurve-style pitch.

“He worked diligently on how the ball was leaving his hand and what his thought process was with the pitch. We were able to show him some examples with high-speed footage, and we reviewed some of the pitch data. Through those things, and from subjective feedback from the catcher and his teammates — as well as himself watching the ball flight — he was able to kind of piece the puzzle together.”

Laurila: Any final thoughts?

Jagers: “We’re beginning to peel back the layers of metric-based evaluation. It used to be ‘high spin, throw up in the zone,’ and we found out that wasn’t always true, and that how you spin it is pretty important. Spin direction and true spin reign supreme there. Here’s an example for a fastball profile: An individual with much lower spin rate, but a spin direction closer to 12:00 — high spin efficiency/active spin — can achieve significantly higher vertical break values than an individual who generates a much higher spin rate, but a spin direction further from 12:00 — say, closer to 3:00 or 9:00 and/or less spin efficiency/active spin). We’re learning how little we know about the things thought we already had solved.

“So there’s a lot to consider, and it gets complex quickly. We need to remember a couple things. One, we owe it to the players to be as well-versed on this stuff as possible, to give them the best chance to achieve their dreams and help the team win. Two, communicating complex information in a simple, easy to understand manner is vital. This stuff needs to be digestible and actionable for our players.

“What will we learn next?”

David Laurila grew up in Michigan's Upper Peninsula and now writes about baseball from his home in Cambridge, Mass. He authored the Prospectus Q&A series at Baseball Prospectus from December 2006-May 2011 before being claimed off waivers by FanGraphs. He can be followed on Twitter @DavidLaurilaQA.

newest oldest most voted
Eric Robinson

Great article. I personally am not a pitching minded person but I learned a lot from this article on how to view pitchers. Viewing a pitch as both movement and location with release point mattering in the equation equaling the whole has always seemed to make sense to me and it seems like most of the metrics (at least that I am aware of) tend to view them each individually. I like that a lot.