Luis Severino’s Breakout Season

At this time last year, Luis Severino had just finished up his second minor-league start of the season. It was only his second minor-league start of the season because he had started the season in the majors. But seven starts were all Yankees manager Joe Girardi needed to see before he and the Yankees organization sent Severino packing, first for a start at High-A and then to Triple-A. On June 3, 2016, he allowed three runs in 3.2 innings for Scranton/Wilkes-Barre. Yesterday, a year and a day later, he allowed two runs in seven innings against the Blue Jays. A year after his demotion, Severino is one of the best pitchers in baseball.

Let’s start with his demotion. In his first seven starts last season, Severino threw 35 innings. He allowed 30 runs, 29 earned, for a 7.46 ERA. Yuck. His 5.52 FIP also was unsightly, but showed that his 27 strikeouts against 10 walks painted a somewhat brighter picture. But then there was his 3.98 xFIP, a more or less league average mark. The discrepancy is the result of the eight homers allowed by the Dominican Republic native — six in Yankee Stadium, and two in Oriole Park at Camden Yards. That’s quite a bit for 35 innings pitched. It works out to a 2.09 every nine innings, a mark that has only been achieved twice by qualified pitchers in major-league history — Sid Fernandez in 1994 (2.11) and Jose Lima in 2000 (2.20). So, it stood to reason that Severino wouldn’t keep allowing homers at such a high rate. Or, you could make the argument that only two pitchers had allowed homers at such a rate because usually, when a pitcher is doing that, he’s unlikely to compile enough innings to qualify for the ERA title. Because he’d probably get sent to the minors. Which Severino did.

Severino would work diligently in the minors. After the aforementioned June 3 outing, he would make nine starts. In eight of them, he allowed three runs or less. In the final of those nine starts, he struck out 11 in six innings and got himself a ticket back to the Show. He would make two starts, one in Boston and one versus Tampa, and the results were a carbon copy of his previous major-league work: eight innings pitched, 15 hits allowed, 12 runs allowed, 10 strikeouts, one walk, two homers. He was doing his job in terms of walks and strikeouts, but too many batted balls were finding green pasture or outfield bleacher. At this point, Girardi could be forgiven for not sticking with Severino. And he didn’t. Severino went right back to the minors and didn’t come back up until rosters expanded. When he did, he was a reliever, until the end of the season, when he made a couple of nondescript, short starts.

For the 2016 season as a whole, Severino made only 11 starts. He only reached the six-inning mark in three of them, and only one of those three cleared the bar for a quality start. Fast forward to this season, and Severino has already reached the 11-start threshold. He’s gone at least six innings in seven of them, and all seven have been of the quality-start variety. That is underselling the difference in his seasons.

Last season, Severino finished with a 102 FIP- and 0.6 WAR. This year, he’s posted a 71 FIP- and 1.7 WAR. Last year, of the 273 pitchers who pitched at least 60 innings, Severino’s 0.6 WAR ranked 186th. This year, his 1.7 WAR ranks 12th, and seventh in the American League. That’s pretty good, if you weren’t aware.

Luis Severino has widened the velocity differentials on both his changeup and slider. (Photo: Arturo Pardavila III)

So, how did we get here? Well, various ways. A little here, a little there. One thing that’s interesting is that Severino’s success isn’t a product of him having suddenly learned how to stop fly balls from becoming home runs. For the entire 2016 season, Severino’s home run rate on fly balls (HR/FB) was 16.4%; this season it’s 16.3%, which is, you know, the same. It’s 27th highest among qualified starters. And yet, he has improved significantly, which is impressive.

One way he has improved is by increasing the gap in velocity between his fastball and his other offerings, the slider and changeup.

Let’s look at those differences in tabular form:

Luis Severino, Velocity Differences, 2016-2017
Pitch 2016 2017 Diff
FF-CH 7.33 8.97 1.64
FF-SL 7.91 10.04 2.13

Now, there’s no concrete evidence to suggest what is the optimal differences between fastball velocity and changeups and sliders. Anecdotally speaking, however, a 7 mph differential appears insufficient. Now, Severino is getting a gap big enough to give batters pause. He’s further given them pause by not throwing the fastball as frequently; he’s lowered his fastball percentage by three points, making it closer to a 50-50 proposition that a hitter is getting a fastball on any given pitch.

He’s also been able to generate more whiffs on his slider. Let’s look at the breakdown of his Statcast stats by pitch:

Luis Severino, Statcast Stats by Pitch Type, 2016-2017
2016 2017
Pitch Type Pitches ISO Alllowed Whiffs Whiff% Pitches ISO Alllowed Whiffs Whiff%
FF 697 0.245 63 9.0% 568 0.179 52 9.2%
SL 428 0.127 52 12.1% 424 0.079 73 17.2%
CH 112 0.148 10 8.9% 100 0.137 10 10.0%
SOURCE: Statcast

So, he’s getting the same percentage of whiffs on his fastball, and he’s seen a slight uptick in whiffs on his changeup. But he’s getting a lot more whiffs on his slider. He’s already thrown the same amount of sliders as he did last season, and he’s gotten nearly 1.5 times the whiffs. That’s pretty impressive.

Of course, it’s not just the slider that has performed better. If you look at his ISO allowed for all three pitches, he’s doing much better across the board. One of the reasons for that transformation is that he’s getting more ground balls. Last season, he generated grounders on 45.1% of his batted balls. This year, he’s up nearly 10 points, to 54.5%. That puts him 10th in the majors in GB% among qualified pitchers.

The difference so far in his GB% hasn’t come against lefties, but against righties.

Luis Severino, Ground-Ball Stats by Batter Handedness, 2016-2017
Year Overall GB% GB% vs. LHB GB% vs. RHB
2016 45.10% 46.60% 43.80%
2017 54.50% 47.60% 60.40%

My oh my. And from his Statcast exit velocity numbers, we can see that he is not just getting more grounders, but weaker grounders. Last season, he allowed an average exit velocity of 84.5 mph on grounders, and this year he’s at 82.5 mph. More grounders with a weaker velocity on said grounders is a good recipe for success. So far, his jump in GB% against righties from 2016 to 2017 is the largest in the majors. There have been 82 pitchers who pitched at least 30 innings against righties both last season, and this season. Of them, 12 have upped their GB% against right-handed hitters by at least 7%:

Highest Positive Ground Ball Change vs. RHB, 2016-2017
Pitcher GB Pct Change
Luis Severino 16.67
Alex Wood 14.97
Lance McCullers 10.78
Matt Boyd 9.97
Dallas Keuchel 9.28
Wade Miley 8.47
Daniel Norris 8.14
John Lackey 8.08
Jhoulys Chacin 7.90
R.A. Dickey 7.40
Stephen Strasburg 7.18
Luis Perdomo 7.08
Min. 30 IP vs. RHB in 2016 and 2017

(Hat tip to the venerable Sean Dolinar for this table.)

Judging from where he’s spotting his pitches to righties this season versus last, this doesn’t look like a fluke.

That’s 2016 on the left and 2017 on the right, each from the pitcher’s perspective. You don’t need to be an expert in reading heat maps to see that Severino is working the ball down and away to righties with far more frequency this season.

Put that together, add a dash of maturity, and you have a frontline pitcher. That maturity was on full display yesterday afternoon against Toronto. In the sixth inning, he allowed two very hard hit balls to Kendrys Morales and Justin Smoak. The hit from Morales into the left-center gap would have been a double off the bat of most major-league hitters, but Morales (who seems bigger every time I see him) jogged to first. The hit from Smoak would have been a homer in many ballparks (Home Run Tracker tagged it as “plenty”), and yesterday at Rogers Centre was no exception. His blast tied the game.

Then, leading off the seventh, Severino hit Devon Travis with a pitch. At this point, with the game now tied and the leadoff runner on base representing the potential go-ahead run, the Yankees required some shutdown pitching. The Blue Jays began by helping the Yankees, sac bunting Travis over to second. (It only dropped their win expectancy by 2%, because it was the go-ahead run in a late, close game.) But then Severino got a grounder to short and a fly ball to center and the threat died. The grounder to short moved Travis to third. Severino didn’t care. His first pitch to Kevin Pillar was a slider in the dirt.

Match up these sorts of stats with a pitcher who’s willing to uncork that pitch in the seventh inning with the go-ahead run on third base, and you’ve got a guy who is really feeling it. And the best part is that he’s compiled this impressive start against good competition — nine of his 11 starts have come against the Astros, Cubs or AL East teams.

Before the season, the Yankees appeared to be a club in need of pitching. Their starting rotation ranked just 13th in our preseason Positional Power Rankings, and even the most enthusiastic Severino supporter would have had to admit, given how his 2016 season went, that his was one of the spots that the team would likely have to upgrade. More than two months into the season, New York’s rotation has mostly played to type. They rank 11th in starting pitching WAR, but Severino has gone from weak link to rotation bedrock. If the team can figure out how to get Masahiro Tanaka right, they might not have to trade for any starting pitchers, and Severino is the biggest reason why. The 23-year-old is breaking out in a big way. He’s having the best season of his young career, and is currently one of the best pitchers in all of baseball. Severino is a prime example of why you don’t give up on young players, and the Yankees deserve a lot of credit for standing by their man.

Paul Swydan used to be the managing editor of The Hardball Times, a writer and editor for FanGraphs and a writer for and The Boston Globe. Now, he owns The Silver Unicorn Bookstore, an independent bookstore in Acton, Mass. Follow him on Twitter @Swydan. Follow the store @SilUnicornActon.

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I had a strong distaste for how the Yankees used to do things, but I find myself with growing admiration for how they got to where they are now.

dr. mvn
dr. mvn

It’s kinda silly that they re-tooled and at no point had a losing season along the way.


silly or perhaps skillful?

Mr Cashman has done a helluva job in the last couple of yeras


I don’t want to take anything away from the Yankees but it is certainly an advantage when you can retool while maintaining a $200-$230M+ payroll. That kind of money hides an awful lot of mistakes.

London Yank
London Yank

In some ways maintaining that much payroll while retooling makes things difficult. A lot of roster spots and resources were taken up by unproductive players.

Tim Jackson

It’s been really sound and fun to watch. Severino’s starts kind of epitomize it, too. He gives the impression that he’s going to be a baller and he doesn’t care what the other team wants. It’s awesome.


They spent 1 billion on payroll over 4 years and never made the LDS or won a single playoff game. Sign me unimpressed.

Had a nice start to this year. Part of that is Judge and Severino, but for the most part its unexpected performances from guys like Hicks, Gardner, Castro and Pineda. When regression hits it will hit hard. They are 11-13 over last 24 games with the easiest part of the schedule behind them

Tanned Tom
Tanned Tom

Think I’ll color you ill-informed instead. 54 games and 38 have been against Cubs, Cardinals, Astros or AL East teams. That does not sound like a weak schedule.


Hicks is a former top prospect who is still 27 years old. You could argue he is simply a late bloomer. Gardner and Castro are both having career years but are also not completely ridiculous. Castro has always been a BABIP enigma and has flirted with stardom in years past. Gardner is one of the streakiest players alive and likely to come down. But Hicks and Castro? I don’t know. I could see both of these starts sticking.

Also, the point is that Cash has built this team on the fly without sacrificing too much in general. The Cubs are where they are due to some solid trades and FA pick ups….but also were gifted some #1 picks. The Nats had two straight #1 picks in Harper and Strasburg. They haven’t won anything yet. The Yanks perpetually pick in the latter half of the draft. Much harder to build a farm when you have no prime talent (outside of Blake) when you select between 15-23 year after year. Cash has done an amazing job.