Now that I've asked the question, let's answer it, shall we? Of course, Gray and Ross have many things in common. They are both exciting young pitchers. They both debuted last season. They share a first initial. They both pitch in the National League. They both feature primarily fastballs and sliders. Both of their fastballs were expected to be their best pitch, but it's their sliders that have been elite thus far in their young careers. The most helpful answer, for our purposes, is that both have seen changes in their peripherals and skillset that have been masked by surface stats buoyed or inflated by luck.
For Gray, his peripherals have been elite, but you'd have never guessed it from his ERA, which was above 7 at the time of that writing. For Ross, his peripherals are in decline, but his ERA has remained superb due to some good fortune.
The natural follow-up question is what other pitchers have shown changes in peripherals that have been masked by their surface stats? One answer to this question is Nathan Eovaldi.
You wouldn't know it from looking at his ERA, which has remained at his previously established norm, but Eovaldi's peripherals have taken a substantial turn for the better. His K% has jumped from 18.0% to 22.2%. His BB% has fallen from 7.3% to 5.6%. Between these two improvents, his K-BB% has improved by almost six percentage points, the third largest improvement in the game. He's done this while maintaining a plus groundball rate (51.9%).
Why are these improvements not showing in his ERA? The main reason is his inflated HR/FB ratio, which sits at 17.9% (career 7.7%). You could argue that 7.7% mark has been pretty fortunate, and it'd be hard to disagree, but 17.9% is way too much of a swing in the opposite direction to be sustainable. Only 6 qualified pitchers since 2002 have run a HR/FB ratio that high over a full season. His BABIP has also been inflated (.328), but he does have history of high BABIPs (career .317), so that is less of an impact.
Now, his peripherals are nice (3.40 xFIP), but how's he getting them? What's he doing to earn them?
For one thing, he's averaging 96.7 mph on his fastball (the 2nd fastest average velocity in MLB among starters), but he averaged 96.6 last year, so that's not the reason for his improvement (though it is a nice testament to his potential). The whiff rate on his fastball has also remained identical, as has the movement. The pitch has shown some improved performance, generating a great 49% GB rate, as opposed to 44.2% last year, but it's not the reason for the improved K%.
The reason for his K rate improvement is quite simple, actually. He's getting ahead in the count more often (58% of his batters faced have gotten to a 2-strike count this year, as opposed to 51% last year) and he's doing a better job putting guys away (38.1 K% after two strikes this year, versus 35% last year). Neither of these changes have been dramatic, but between the two it's resulted in a substantial K% spike. Is it sustainable, though?
To answer that question, I think it's best to separate the two improvements and evaluate them separately. First, the improvement in getting ahead in the count. It's backed up by a spike in Zone% from 47.7% to 51.6%, as well as a massive spike in first pitch strike% from 59.7% to 66.1%. He's going after batters substantially more than he has in the past. He's not messing around nibbling at corners. He's going right after you. Such a monumental change in approach is more than enough to explain the spike in 2-strike counts.
But what about his improved efficiency in putting batters away after reaching two strikes? Is that here to stay as well? There's no definitive way to answer this one, but I believe there's evidence indicating it is. First, he's doing a better job fooling hitters, regardless of count; his Fool% (a metric I invented that measures how often a pitcher gets a batter to take a pitch in the zone or swing at one outside of it) is up from 30.9% last year to 33.6% this year. Second, he's changed his pitch mix with two strikes dramatically. He's cut his two-strike slider usage in half and is throwing less fastballs in favor of the splitter, which he's now throwing nearly half the time in two-strike counts. That's a ton of confidence for a pitch he just started throwing last season[LINK]. Take a look at his pitch mix with two strikes from last year to this year (2015 first, then 2016):
Now, between the improved ability to fool batters and the drastic change in pitch mix with two strikes, I'd say we have enough evidence to accept his improved efficiency with two strikes as the new norm, though it's something to continue to keep an eye on.
As for the walk rate improvements, we've already covered how he's attacking hitters early in counts and getting ahead, and that's more than enough evidence for me to buy into his improved BB%. In fact, I wouldn't be shocked to see his walk rate continue to fall.
More on that splitter: Eovaldi only began throwing a splitter in 2015, hoping it would be the answer in his quest to find a reliable changeup. He steadily used it more and more throughout the season (see image below), and it slowly became his primary offspeed pitch.
The pitch itself was evolving as it's usage increased, as Eovaldi made a minor tweak to the grip that improved both the velocity and movement of the pitch, as demonstrated below (courtesy of Rob Friedman aka @PitchingNinja):
Here's a first-hand look at the pitch itself:
That certainly looks like a good pitch. In a short time, the splitter has gone from a new pitch for Eovaldi to his out-pitch. It's certainly earned it's increased usage, accounting for 68% of his strikeouts.
Combine the development of a plus splitter with increased strikeout ability, a falling walk rate and his typical groundball tilt, and we may have a true breakout on our hands.
With Eovaldi, we've got another case of a guy showing serious skills improvements that are being masked by bad luck in the BABIP and HR/FB departments. Don't be fooled; those will correct and the skills will shine through.
Verdict: He may not be an ace, but Nathan Eovaldi has shown marked improvement that should make him a great guy for the middle of your fantasy rotation. He could finish as a top-40 SP - if not higher.