Nathan Karns is currently competing with James Paxton for a spot at the back end of Seattle’s starting rotation. The 28-year-old right-hander has the potential to be more than a No. 5, however. Acquired by the Mariners from Tampa Bay in November, Karns has a big fastball, a power curveball and a much-improved changeup. In 27 games last year, he logged a 3.67 ERA and struck out 145 batters in 147 innings.

Karns has a studious approach to go with his raw stuff. That much was evident when the Texas Tech product broke down his repertoire and his pitching philosophy earlier this week.

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Karns on his approach: “I focus my pitching on the lineup I’m facing. I kind of preplan. I identify weaknesses and strengths, so that I can go in with a plan for each hitter. I’ll get their numbers. First-pitch swinging is one. Do they swing at first-pitch curveballs? I’ll keep little things like that in the back of my mind.

“The count and runners on base come into play. So does what I’m working with on a given day. For instance, if I can’t throw my curveball in the bullpen before a game, I’m not necessarily going to run away from it, but it might not be my No. 2 pitch that day. What I’m executing may cause me to adjust.

“It’s important to be aggressive. If you’re not — if you’re playing on your heels — it’s going to be tough. Put the pressure on the hitter. If you execute your pitches, it’s going to be difficult for him to tee off. You want to attack, work ahead, and mix up your speeds.

“I like to force hitters to swing early. In the past, I’ve found myself throwing five, six pitches per at-bat, so by his third at bat, a hitter has seen it all. He has a really good idea of what I’m trying to do and how my ball plays. If I can cut down on how many times someone sees my pitches, I should be more effective.”

On his curveball: “I’m lucky in that my curveball doesn’t have much of a hump in it. I can disguise it on certain days. If I’m feeling really good, I can kind of keep it straight and have it dive at the end. Eliminating that hump has allowed me to throw the pitch more often; it gives me the flexibility to throw it in different counts. It comes out of my hand similar to a fastball and then will bottom out. Some people call it a slider with straight down tilt. With my arm slot and the way I throw it, it gets the depth it needs to be a considered an out pitch.

“The grip is along the lines of a slider grip. I think that’s what allows me to throw it a little harder. I actually spike it. When I slide my index finger up, it pushes the ball tighter into my fingertips. It may not feel good for you, but it works for me and that’s all that matters.

“Grips are just something you play with. It’s about comfort level. There have been times I’ve switched the curveball, trying to find feel for it. Then you go back to it, and there it is.”

On locating his curveball: “I’m able to throw a curveball that looks like a fastball up and out of the zone, then falls into the zone for a strike. If I’ve established my fastball up there, I can throw my curveball in that same zone and they’re going to hesitate. They’re going to pick it up like a four-seam and give up on it.

“Same thing if I can keep my fastball down, and then throw the curveball in the same spot. That’s where I get a lot of my strikeouts. It’s about angles and planes.”

On mixing his four-seam and two-seam fastballs: “I can’t consistently throw four-seams up. It’s one time to a hitter, usually, at least. But it depends on the situation. For righties, I like the two-seam down and in. Same spot to lefties. The two-seam is more of an arm-side pitch, although I may get fancy with it on days I have really good feel. I might go front door to lefties. But for the most part, it’s glove side and throwing my the changeup off of it in the same window. With the four-seam, I’m low, high and will let the curveball play off of those.

“You have to establish a pitch. If I can establish a two-seam low and away, that opens the door for a changeup there. If I haven’t established my two-seam low and away, if I go to the changeup, he may not swing — he hasn’t seen me locate there. Everything plays off of your fastball.”

On his changeup: “Last year it became a consistent weapon. In the past, I was able to throw it successfully at a very low rate. It was more of a show-me pitch. Now I have a better feel for it and know how it plays. I know the action on it. Because of that, I’m able to throw it in smaller areas.

“I didn’t (change anything). It was just more years, more reps. Now that I understand it better, I’m not trying to make it do something it’s not going to do by itself. Instead of trying to manipulate the pitch, I’m just finding the starting place and letting the action run its normal course.

“It’s a two-seam, kind of an offset two-seam. I put it deep. I like to push it a little more toward the pinky. I kind of push it in a way that I feel tension in the pinky. It plays off my two-seam. Same grip, same action, so for lefties I have two-seam movement away. It’s the same spin as my two-seam, so hopefully they read two-seam and not changeup.”

On inducing weak contact and speed differential: “That big drop (on a changeup) takes more feel than I currently have, but I’m pretty happy with it being more of a rollover pitch. I can use it to throw hitters off rhythm, and I get ground balls with it. That’s good, because I prefer to pitch to contact and get shorter at-bats and quicker innings.

“For me, it’s more about having the same arm action as my fastball. I may not necessarily be throwing it 100%, but I’m throwing it with enough conviction, enough arm action, that it looks like a fastball coming out of my hand. I want them to read fastball, then when they start to swing, the ball starts adjusting its course and drops out of the zone. I’m still working on it. At times it does more of a power fade, but I’m… if you look at a clock, I’m trying to get straight down to six. Right now, it’s more like five or four.

“Last year it was 84 to 88 [mph]. It was in that window. It’s not a pitch where I can sit there and match the same speed every time. My fastball is 91 to 95. I think how much [differential] is different for each person. If you look at Felix Hernandez, his is in the upper 80s and closer to his fastball. It’s what works best for you. Once you’ve found something comfortable, it comes down to executing it and repeating it.”

On joining a new team and not overthinking: “Everyone is new here, so we’re still getting a feel for each other. [Pitching coach] Mel [Stottlemyre] is still getting a feel for what I like to do and I’m getting a feel for how Mel likes to do things. With mechanics, it’s more of me trying to find a rhythm. Right now I’m kind of quick, so we’re working on slowing everything down. We’re trying to minimize… maybe not minimize, but make a difference in my effort level, through my mechanics. My first half has been quick, and probably too amped up, so we’re focusing on my effort and my tempo.

“I like to keep things easy. I can definitely overcomplicate things — make things tougher in my head — at times. Simplify. That’s why I don’t have a bunch of movement in my windup. I’m more about taking it easy. If you keep it simple, it should come out simple.

“There is [a lot of thought behind the simplicity]. You can frustrate yourself trying to get to that point. For me, it’s a process. You have to come in each day knowing what you’re working for, and what you’re trying to get out of what you’re trying to do. I’ve been doing some towel work, some mound work, trying to find my rhythm so that I can feel comfortable on top of the mound. If you don’t feel comfortable when you’re toeing the rubber, it’s going to be a tough day.”

On learning from a former teammate: “I’m more of a visual learner. I stand back and observe how people go about things. I don’t want to wear people out with questions. I’ll watch, and if I see something, I’ll keep that question and ask them later.

“My locker in Tampa Bay was next to Chris Archer’s. Every day he had something to do. He knew what he was doing and what he was going to get out of it. He stayed consistent and didn’t skip days. The guy has talent most people don’t, and his work ethic allows him to maximize that talent. That rubbed off on me. My day isn’t the same as his —everyone is an individual — but I come in every day trying to get better. I focus on what I need to do.”