Things have gone very smoothly for Luis Severino. Since his first stint in the United States with the Gulf Coast League Yankees in 2012, the closest thing the 21-year-old righty has seen to difficulty as a player was when he had a 4.08 ERA over all of 17.2 innings at Low-A Charleston in 2013. This year, he continued to jump up the system, making 11 starts for the Yankees with a 2.89 ERA.
Severino rocketed through the farm system and hit the ground running when he reached The Show. But if he had not pitched as well as he did in the big leagues, one thing would have stood out: his declining strikeout rate. After routinely striking out more than one batter per inning at lower levels, Severino struck out just 7.34 batters per nine innings over 11 starts at Triple-A. In major league pinstripes, that figure was bumped back up to 8.09.
Obviously, major league hitters are a lot better than batters in Double-A. But in an ironic turn of events, the drop in strikeouts at Triple-A may be a result of him fine tuning one of his pitches. In a preseason scouting report, Fangraphs' Kiley McDaniel had this to say about Severino's slider:
The concern is that he's throwing one pitch and, in the 2014 outing in the video, the velocity of it ranged from 82-91 mph, looking like a cutter, slider and a hybrid third pitch between them. He "accidentally" threw a 91 mph pure cutter one time in the outing that was plus, further underlining the arm talent but lack of feel for how to consistently spin the above average breaker that he clearly has in there somewhere.
As we now know, that offering now looks like the 91 mph cutter. That pitch is also known as the "Dan Warthen Slider," a pitch named after the Mets pitching coach and observed by Eno Sarris at Fangraphs. Mets pitchers like Matt Harvey, Jacob deGrom, and Jeurys Familia all throw their sliders at around 90 mph, as opposed to the traditional slider, which sits in the mid 80's and features more movement. Evidently, the Dan Warthen slider is easier to command. But pitchers who throw slower sliders can generate Whiff/Swing ratios north of 50%. Even elite pitchers like Harvey and deGrom can't generate those kinds of numbers with their modified sliders.
It is possible that Severino decided once and for all to tighten up his breaking ball during the season, causing the reduction in strikeouts after he reached Triple-A. The good news is that Severino's slider serves its purpose. Opposing batters hit just .234 against the pitch with a .351 slugging percentage. The better news is that Severino is just 21 years old and still has plenty of time to add a curveball to his repertoire.
Adding a good curve would serve two purposes. First, it would give him another out pitch. Secondly, it would give Severino the chance to change speeds in a way that he can't right now. Even his changeup, his best offering, is usually thrown in the high 80's, and it prioritizes movement over separation from his fastball velocity.
If the reason for Severino's decline in strikeouts is because he decided to stick with a power slider, it would mean that he still has more improvement to do before he reaches his ceiling. The fact that he has broken into the big leagues suggests that his hard slider has developed into a plus pitch. Furthermore, considering how well he has already done, knowing that Severino still has significant room for improvement is very exciting. Luis Severino already figures to be an integral part of the 2016 season, but he is also just one more breaking pitch away from something much more special.
*All data is courtesy of Fangraphs and Baseball Prospectus.