How Paul Sewald Learned His New (and Really Good) Slider in Seattle

Paul Sewald
Steven Bisig-USA TODAY Sports

The Learning and Developing a Pitch series is back for another season, and we’re once again hearing from pitchers on a notable weapon in their arsenal. Today’s installment, presented in a Q&A format, features Seattle Mariners reliever Paul Sewald on his slider.

Since signing with Seattle as a free agent prior to last season, Sewald has won 12 of 16 decisions, logged 15 saves, and has a 2.86 ERA, a 3.20 FIP, and 123 strikeouts in 85 innings. The 32-year-old right-hander has thrown his signature slider — a pitch he completely revamped after coming over from the New York Mets — 42.8% of the time.


David Laurila: You’ve developed a great slider. What’s the story behind it?

Paul Sewald: “Since the beginning of time — before TrackMan, before Rapsodo, before everyone realized exactly what the pitch does — every pitching coach in the history of the world said, ‘You need two planes on your slider, you can’t have it go just sideways. That’s not how you get outs.’ So that’s what I thought. I tried to make it have two planes.

“When I first started throwing it, it was very slurvy. It wasn’t very hard, but it did move in two planes. It wasn’t a curve. It wasn’t a slider. It was somewhere in the middle. That’s how I grew up throwing it, and I always went back to that line of thinking. Slurvy or not, it had to have two planes.

“Then I got over here to the Mariners and it was, ‘We don’t care if it moves one centimeter down, we just want you to sweep it as far as you can possibly sweep it.’ I said, ‘OK, that’s interesting. I haven’t been trying to do that, but I throw across my body, so it seems like something I could do.’

“Immediately that worked. It was overnight. In camp last year, I didn’t pitch very well, but that was because of my fastball. The slider was very good. As soon as they told me, ‘We don’t care about any depth, we just want sweep,’ I took off with the slider. It was a very easy and very comfortable switch for me.”

Laurila: Outside of having the right delivery — throwing across your body — how did you go about getting the action the Mariners were looking for?

Sewald: “I think it was more of a mentality thing. I feel like I was trying to loop a slider in there to make sure that I got two planes. Now I literally just grab it and throw it as far over to the right as possibly I can, bringing it over to the left as far as I possibly can. For me, it’s more of a mentality pitch than anything. There is no get-me-over aspect to it at all. I try to throw it as hard as I can every time, yanking it glove side as much as I can. “

Laurila: Intent is a big key.

Sewald: “Yes. There was definitely an intent and effort change when I started working on it. It was, ‘Let’s just make it spin as much as I can to the left. How do I do that? Well, I think I need to throw it harder.’ Basically, I needed to let it really eat every time. I didn’t want to be a throwing a get-me-over slider.”

Laurila: The spin axis would have needed to change in order for you to get all horizontal.

Sewald: “You know what? I’m sure my spin axis changed, but that’s because of the way I was trying to throw it. Maybe subconsciously… I started getting literally just on the side of the ball, instead of on top of it, to try to get a little bit of depth. But really, I grip it the same way. I grip the same slider I’ve had my whole life, I’m just trying to sweep it as much as I can. ‘Yank it left’ is essentially all I’m thinking.”

Laurila: Have you compared then and now on an Edgertronic?

Sewald: “We did Edgertronic when I was in New York, and it was kind of interesting to watch, but I haven’t done it since I got here. It’s been kind of an if-it-ain’t-broke-don’t-fix-it thing. I’ve been throwing well, so I haven’t had to go back to a drawing board and figure anything out. I also know that our pitching group is on it. If we do end up needing to go back to a drawing board, they’ll make sure that it happens. And that’s part of the reason I love Seattle: they’re on top of anything and everything, just in case you need or want it.”

Laurila: How did New York compare?

Sewald: “I think they were a tad behind the Mariners.”

Laurila: To my understanding, a number of teams are.

Sewald: “Yes. And that’s part of why I came here. When I was a free agent, I was looking at Toronto, Houston, and Seattle. My agent said to me, ‘You know, Seattle has had very good pitching-lab development. They’ve taken a couple of non-roster invites and turned them into better pitchers.’ That’s all I was hoping for. I hadn’t even imagined becoming one of the best relievers in the American League, I just wanted another chance in the big leagues. I was expecting 1% better, maybe 10% better. I wasn’t expecting 100% better.

“The very first meeting we had in spring training, they told me that I get my slider to sweep 15 inches 20% of the time. What was I thinking when I did that? I told them that I didn’t really know, that I didn’t really have a game plan. They said, ‘OK, let’s see if we can get you to sweep it 15 or more inches 50% of the time. Then we’ll go from there.’

“Could I have gotten the same information from the Mets? I think I could, but they weren’t offering it to me, I probably would have had to seek it out, and I wasn’t even sure what I needed to seek out.”

Laurila: You mentioned Houston and Toronto earlier. Did you reach out to those teams when you a free agent, or did they approach you?

Sewald: “My agent sent stuff out to all 30 teams, and those two, along with Seattle, were the most interested. I was like, ‘OK, Seattle’s had a great reputation, Houston’s had this outrageous reputation for success, and Toronto looks like they’re on the move. There must be something I do really well that good teams want, because these are good teams and they want me. Let’s figure out exactly what it is.’ That’s what happened. The Mariners helped me figure it out.”

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.

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5 months ago

That’s a terrific interview – surprisingly interesting and inciteful stuff. I’ll just add, David, that you do a really nice job of parsing through the words said and adding the correct punctuation – that is an under-appreciated art that takes effort and careful thought to get it right.

One suggestion: would have loved to see a GIF of that big sweeping slider in action, perhaps contrasted with one from his Mets days.

Last edited 5 months ago by LenFuego