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Player profile: Kevin Jepsen

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The hard-throwing righty should continue his dominance in a Rays uniform.

Kim Klement-USA TODAY Sports

Acquired during the offseason by the Rays, Kevin Jepsen is getting more focus here on DRays Bay after having his pitches analyzed by Ian Malinowski and his place in the bullpen figured out by me earlier in the month. As said in those articles, Jepsen had a career year in 2014 with a 2.78 FIP and 10.38 strikeouts per nine innings.

Ian brightly exposed the fact that his record year was essentially due to his new use of the changeup and the departure of his cutter. A wise decision for Jepsen which led us to think that the former Angels pitcher can very well reproduce his 2014 performances in the future. Though, while comparing the 2014 Kevin Jepsen to the rookie one who pitched for the Angels in 2009, I noticed a slight difference in his mechanics which might also explain his recent success.


In his Raising Aces column last December, the great Doug Thorburn examined the best and worst mechanics of the American League West. Kevin Jepsen was graded as having the worst balance of his division, with a 35 grade. A negative point that causes him to have "poor repetition" and also "shaky pitch command", even though he has a "strong posture". By comparing the 2009 Jepsen with the 2014 version of himself, we can indeed see his nice posture and even an improvement over the years.

Kevin Jepsen Posture

As Doug Thorburn said, Jepsen does have a strong posture, one that he almost always had but got even better in the recent years. There might be here another explanation of his great 2014 numbers, especially his career-high strikeouts per nine and his below-career-average walks per nine (3.18).

A better posture and a new pitch made Jepsen one of the best late relievers in the game last season, but how exactly did hitters react to his changeup?

Jepsen Heat Maps

With the two heat maps presented above, it is safe to say that hitters were dominated by Jepsen's changeup in 2014. They were unable to hit properly (.182 BABIP on his pitches), and above all they chased and missed it a lot. This may also explain why hitters who faced him made contact way less often when swinging at pitches thrown outside the zone.

Season O-Swing% Z-Swing% Swing% O-Contact% Z-Contact% Contact% Zone%
Career before 2014 27.13% 65.12% 46.17% 60.83% 88.53% 80.05% 50.03%
2014 30.40% 65.80% 47.20% 51.20% 86.20% 74.40% 47.60%

To add to this enthusiastic report, it is also worth noticing that Kevin Jepsen also had a very strong fastball in 2014 with an average velocity of 95.8 mph, just above his career-average of 95.7. According to FanGraphs, his four-seamer had a 9.5 mph speed differential with his changeup. While it could be worse, there is room for improvement here as a bigger gap between his two pitches would probably improve his metrics.


Predictions for the upcoming season aren't very good for Kevin Jepsen. According to Steamer, ZiPS and PECOTA, he will regress in 2015.

Season Team IP K/9 BB/9 HR/9 FIP WAR
2014 Angels 65 10.38 3.18 0.55 2.78 0.9
2015 Steamer 55 9.59 2.91 0.77 3.18 0.4
2015 ZiPS 56 9.48 3.38 0.80 3.31 0.4
2015 PECOTA 60 8.70 3.60 0.75 3.48* 0.5

Please note that ZiPS projections were released while he was still an Angels pitcher, and due to the lack of FIP in PECOTA's projections, the 3.48 mark refers actually to his projected ERA. Despite those numbers, there is more than one reason to think that Jepsen will be at least as good as he was in 2014. Let's break down those predictions, and see what we can realistically expect from him.

Steamer is the only system that predicts a better walks per nine innings ratio in 2015 for Jepsen. Considering his improved posture, and the increase in whiffs per swing on pitches thrown outside the strike zone, we can argue that he will indeed improve his BB/9 ratio. Furthermore, as presented on the pitch location table, hitters chased more his pitches thrown outside the zone, without much success. In fact, he improved his O-Swing% every year since 2011, while having his best O-Contact% since 2009 (51.2% v. 48.8%).

Season IP O-Swing% O-Contact% BB/9
2011 13.0 20.20% 75.00% 6.23
2012 44.2 27.70% 65.00% 2.42
2013 36.0 29.10% 71.30% 3.5
2014 65.0 30.40% 51.20% 3.18

Such numbers do not automatically imply a correlation, nor are they perfect for predicting Jepsen's future, but they are useful to understand why we can expect an improved BB/9 ratio from him in 2015.

Regarding the strikeouts per nine innings, it is legitimate to predict a regression, since he had a career-high in 2014. Nonetheless, behind his 10.38 mark, there are indicators that Kevin Jepsen can reproduce his performance this year. Indeed, he posted his second best swinging strike percentage and his career-high first pitch strike percentage last season. The latter is especially interesting, considering that first pitch strikes relates positively with a pitcher performance. During the last year, the league average for this metric was 59.8% among relievers; Jepsen, with his 65.40% sits well above it. Actually, Jepsen improved his performances regarding this statistic in the past three years.

Added to the increase in swinging strikes, there is room to think that he definitively gained more control over his pitches and should continue to do so in 2015.

Season IP First pitch Strike% Swinging Strike %
2008 8.1 52.8% 7.4%
2009 54.2 58.7% 12.3%
2010 59.0 62.1% 9.8%
2011 13.0 54.4% 6.2%
2012 44.2 51.7% 8.7%
2013 36.0 53.7% 8.6%
2014 65.0 65.4% 11.6%
Total 58.7% 10.1%

Last but not least, let's not forget that he will pitch for a team other than the Angels for the first time in his career. After being once viewed as the potential future Halos closer, Jepsen will now probably be the main setup guy for the Rays. According to ESPN Park Factors, the Angel Stadium of Anaheim was more favorable to pitchers than Tropicana Field in 2014, yet only by 0.083 runs, which is not that huge. So the park won't help Jepsen probably, but how about the Rays team, and especially the catchers?

When he was still pitching for the Angels, Jepsen used to be teammates with Hank Conger and Chris Ianetta, the two main catchers for the Halos in 2014. Using Baseball Prospectus statistics for catchers, especially "Extra Strikes" and "Framing Runs Added by Count" which represent respectively the number of pitches outside the zone called strikes and the number of runs added thanks to catcher framing, let's see how the two compare to the 2015 projected Rays catcher, Rene Rivera.

Framing Chances Extra Strikes Framing Runs
Hank Conger 4540 169 25.2
Chris Ianetta 6213 -19 -2.9
Rene Rivera 4888 176 26.2

As you can see, and probably already wondered, Rivera has nothing to envy to Ianetta and Conger. In fact, Rivera was the second best catcher in the league in 2014 according to these metrics, just behind Buster Posey. If Tropicana Field won't help Jepsen, at least there is good hope that Riviera will be a great asset to him in 2015.

Overall, I think that the current predictions for Jepsen are a bit too pessimistic, since his 2014 performances are explained by multiple factors and there is no reason to think that he will automatically regress in 2015, barring injury.