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Nate Karns, a pitcher on the rise

The Mariners have a new pitcher with some promise. How high is Nate Karns's upside?

Kim Klement-USA TODAY Sports

It’s been almost a week since Jerry Dipoto pulled the trigger on his first trade as the Mariners’ new GM. Like Jack Zduriencik before him, Dipoto’s first trade is a memorable one, not because of the return the team received but because of the names that are gone from the roster. Brad Miller and Logan Morrison endeared themselves to this fan base for very different reasons, but the emergence of Ketel Marte and the presence of Mark Trumbo pushed Miller and LoMo to the fringe of the roster.

What’s done is done. Sam has already covered the two prospects that came back in the trade, Boog Powell and CJ Riefenhauser. In short, they’re both interesting pieces but not the centerpiece. No, the big name the Mariners received from the Rays is right-handed starter Nate Karns. In his first full year in the majors, Karns accumulated 1.5 fWAR and posted a 3.67/4.09/3.90 pitcher slash line. That would be very promising except for the fact that his 28th birthday is right before Thanksgiving.

Karns was originally drafted out of Texas Tech by the Washington Nationals in the 12th round of the 2009 draft. Shoulder surgery delayed his professional debut until 2011 but a strong minor league career led to his major league debut just two years later. He made five spot starts between the Nationals and the Rays before this year when he filled in for the Rays’ numerous injuries. He made 26 starts in 27 appearances and put up some very encouraging numbers before being shut down at the beginning of September with "forearm tightness."

Nate Karns (2015)

















Just a cursory glance and we can start to paint a pretty full picture of Nate Karns, major league pitcher. His strikeout rate is well above average and that’s supported by his strong whiff rate and a 27.7% strikeout rate during his minor league career. He’s always struggled with his command and his walk rate has suffered because of it. As a fly ball pitcher, he’s also had to deal with a case of dinger-itis.

Let dig into his pitch arsenal to see if there’s anything lying beneath the surface that might encourage us even further. Karns relies on four different pitches and two of them are very promising.





92.9 mph;


92.7 mph;


86.2 mph;


81.8 mph;


His curveball is probably his best pitch. It’s a power curve with a significant amount of drop making it fairly unique among right-handed starters. He’s one of ten pitchers who throw their curveball faster than 80 mph with more than six inches of vertical drop. He’s able to generate an above average amount of whiffs with the pitch and he uses it as his primary out pitch.

I used the word probably above because Karns has improved his changeup by leaps and bounds. Eno Sarris from FanGraphs called his changeup the most improved pitch in all of baseball after the first half of 2015. This graph illustrates the improvement very simply:

Karns CH VMov

As the season wore on, Karns’s changeup gained more and more vertical drop (remember vertical pitch movement is calculated in comparison to a hypothetical pitch with zero spin). By the end of the year, he was throwing a changeup with a speed and shape similar to Jacob deGrom’s and Corey Kluber’s changeups. He generated an above average amount of whiffs with the pitch and batters hit just three extra-base hits off of it all year.

With two above average secondary pitches, Karns has two weapons that will help him stick in any major league rotation. Here’s the rub though, his fastball is just average. He throws it with just average velocity and it’s very straight. It does have an incredible amount of "rise" to it, the seventh highest vertical movement among all right-handed starters. It’s very similar in speed and shape to Chris Tillman’s fastball. He’s able to generate an above average amount of whiffs with the pitch, but he’s leaving the pitch elevated too often. Here’s his zone profile with isolated power against him highlighted:

Karns ISO

You see that giant red mark right in the middle of the zone across the letters? Batters have punished Karns when he throws there. When he throws inside and elevated to right-handed batters, he gets punished. Almost three quarters of the home runs he allowed last year came off the fastball and most of them came off pitches elevated in the zone. Yes, his fastball generates an elite amount of "rise" but it doesn’t have the velocity and he doesn’t possess the command to maximize its value.

Karns’s success hinges on his ability to limit damage via the home run. Moving to Safeco Field should help a bit but he is the master of his fate. The improvement of his changeup is very encouraging, not only because it gives him another above average pitch, but also because it shows his willingness to work towards improvement. He will likely take the fourth spot in the Mariners’ rotation this year. He has the tools and the arsenal to be a very successful pitcher in the major leagues. He has the upside of a number three starter on a good team, but he won’t reach that potential unless he’s able to improve the command of his fastball.