The Z Files: Five Surprise Arms

As many of you know (and if you don't, you're missing out on some cool content), I administer a weekly Tout Table where I pose a question to the 94 participants. Anywhere between a quarter and a half of the group responds and I post the answers on ToutWars.com.

This week's query was:

Which surprising arm has the greatest likelihood of maintaining success and which is slated for the biggest fall among Matthew Boyd, Danny Duffy, Taijuan Walker, Huascar Ynoa and Kyle Gibson?

I started to do the research for my answer when I realized it would make a nice Z Files, so here we go.

Before diving into the players, here's my approach. The first step is comparing actual ERA to ERA estimators as well as getting a feel for luck-oriented metrics such as BABIP, LOB% and HR/FB. For some, it ends here with the luckiest most likely to fall and the one whose actual ERA most closely matches the estimators deemed "for real."

For me, this is just getting the lay of the land. A fortunate hurler can fend off regression via improving skills. A pitcher whose skills support his early success may not be able to maintain them. Perhaps he's benefited from an easy early schedule or has faced teams missing their top players. To consider a skills change sustainable, I want to see something different from previous seasons. This can be added velocity or spin, a new pitch or different usage of his usual repertoire. Usage can be pitch mix, or when in the count he throws each pitch and location. Keep in mind one of the main areas strikeouts are up is on pitches thrown up in the zone.

With that as a backdrop, here is a review of each starter in the order the question was posed (which was arbitrary). All stats are through Wednesday, May 12. I'll rank then at the end.

Matthew Boyd, Detroit Tigers

To be honest, "he's been lucky" is going to be a common theme. In Boyd's case, it's all about the homers. Over the past few seasons, he's been one of the most philanthropic pitchers on the planet. So far, he's seen one ball leave the yard in 41 2/3 frames.

Here is a look at Boyd's strikeout and walk metrics.

Friends, unless Boyd picks it up in the swinging strike department, he's in trouble if the homers revert to previous levels. Keep in mind F-Strike% (First Pitch Strikes) correlates better to low walks than it does high strikeouts.

Is Boyd doing something different with his pitches, helping to limit homers at the expense of strikeouts?

The lefty has upped changeup usage at the expense of his fastball, but not nearly enough to account for the huge drops in homers and punchouts. I'll spare the tables and simply note Boyd's velocity is similar to previous seasons but he's more often working lower in the zone. While the latter corroborates the lower homer and strikeout rates, again the extent of the early-season drops are more extreme than throwing four percent fewer pitches in the upper third.

If Boyd continues to work more in the lower third, the home run correction should not result in the plethora of dingers he's allowed in the past. However, there's a chance his strikeouts do not revert to past seasons, signaling trouble for the Motown lefty.

Danny Duffy, Kansas City Royals

Like Boyd, Duffy is benefiting from a low HR/FB mark. However, unlike his fellow southpaw, Duffy has ramped it up in the strikeout realm.

The catch is Duffy's added dominance isn't backed by the underlying metrics, as his swinging strike rate is low and the small bump in called strikes doesn't not account for the big spike in K%.

Duffy has shuffled his pitch mix a bit, but it is close to that of prior campaigns and very well may not be by design. However, he has gained at least a tick of velocity across the board and is locating differently.

Added velocity and more offerings in the upper third of the zone support the spike in strikeouts. If Duffy continues along this path, there is a good chance his swinging strikes is the metric that moves, even though K% usually shifts towards it and not vice versa.

Both Boyd and Duffy are likely to allow more homers, but of the two, Duffy's skills are better suited to absorb the damage, at least as currently constituted. The caveat is Boyd usually fans more than his 2021 rate while Duffy has picked up his pace and it's not clear he'll maintain the velocity upgrade.

Taijuan Walker, New York Mets

It doesn't require a PhD in common sense to see a logical trend forming. With more runs than ever scored via the home run, pitchers suppressing the long ball are enjoying the most success. That said, Walker is also benefiting from a low BABIP. How are his skills?

Remember, Walker missed almost all of 2018 and 2019 so instead, 2017 is included, but that limits the comparisons to past seasons since 2020 was not only abbreviated, it was his first healthy year post-rehab from Tommy John surgery. Still, an uptick in swinging strikes and the corresponding increase in K% is encouraging, though the added walks temper excitement. Walker's low BABIP has limited traffic despite the bump in free passes.

Let's check out Walker's current repertoire.

He's throwing a lot more off speed and breaking stuff, bagging his cutter in lieu of a slider accounting for much of the change. This goes along with the jump in whiffs as the slider generates more swings and misses, plus offspeed in general is amplifying strikeouts.

There are a few things that make putting everything together for Walker difficult. For starters, the zone percentages from 2017 don't sum to 100% and I can't identify the discrepancy. That said, at least compared to last season, Walker is throwing in the lower third more frequently.

Speaking of last season, the rule of thumb is Tommy John recoverees need a full season before they can be truly judged. The problem is while it was a calendar year, last season was essentially two months in baseball time, so it's unclear whether Walker is back to his true form.

Something not discussed at all yet is team context. Walker benefits most from his home park as Citi Field is the absolute best venue for arms in the league. It suppresses runs more than anywhere else, as well as knocking down homers while embellishing strikeouts.

All told, I honestly don't have a great feel for Walker's prognosis. His baseline expectations are up in the air after two missing seasons and only a partial campaign in 2020. The skills bump syncs with the park effects. Citi Field will soften the inevitable blow, but there isn't enough here to be confident he won't regress to the 4.00 ERA level as suggested by his xFIP and SIERA.

Huascar Ynoa, Atlanta Braves

This is intriguing, as we have the first instance of an unlucky home run rate. Ynoa's good fortune is derived from an unsustainable left on base mark. That said, his ERA estimators are the best of the hurlers dissected so far. That must mean his skills are strong, right?

As expected, Ynoa's K-BB% is stellar. For what it's worth, 2020 is included despite just 21 2/3 stanzas. The caveat to this data is his swinging strike level is a little out of whack with the lofty K%, as he's relying on a high called strike mark and there's no telling if he'll be able to maintain that over the course of the season since prior to this breakout, Ynoa did not display anything near this ability. Sure, the party line was he had good stuff, but there was no indication he'd harness it in this manner.

Let's take a look at that stuff.

The velocity is certainly there, but he's essentially a two-pitch guy reliant on a slider for success. The good news is there is an appreciable delta in velocity between his two main offerings. Even so, once the league gets a book on the 22-year-old righty, he may not be as effective.

Even though Ynoa's ERA estimators are the most encouraging, it's a leap of faith trusting he'll maintain his current skill level with only a two-pitch arsenal.

Kyle Gibson, Texas Rangers

Despite favorable ERA estimators, my hunch is the Touts identify Gibson as least likely to maintain his current pace, and they be right. Let's see.

Outside of one encouraging trend, it appears last season was the outlier and Gibson is the same guy he's been for a few seasons. The catch is he's enjoying more called strikes, which could lead to a small bump in K%, though it has not manifested to date. Is he doing something differently this season?

It looks like Gibson is cutting the ball more while throwing fewer sliders and changeups. Cutters can be effective, but they're not usually strikeout pitches and don't draw many called strikes. The high number of called strikes emanate from Gibson's curve and changeup, which he rarely deploys.

It doesn't feel like Gibson is any different than previous seasons. That said, his ERA in 2018 and 2019 was inflated due to a high number of homers. Pitching in Arlington, where Globe Life Field is suppressing power along with the new ball, Gibson's home run output could fall, keeping his ERA more in sync with his estimators.

Summary

Admittedly, this isn't a comfortable declaration, but I see Duffy's fall from grace the softest. It's a leap of faith he's able to maintain the elevated strikeout mark, but that's my call and I'm sticking to it.

On the other end, I'm waffling between Boyd and Gibson as the hardest fall. I think my lean is Gibson since he doesn't have the strikeout skills possessed by Boyd.

That leaves Ynoa and Walker battling for the second and third spots. As much as I like what I've seen from Ynoa, I'm worried the league will catch up and his pedigree is not in his favor. Plus, as the weather warms, Truist Park will become increasingly hitter friendly.

So by process of elimination, if Duffy isn't able to fulfill the responsibility of being my hurler to incur the least regression, Walker is next in line. This is more of a gut call than I usually rely upon, but the park is very much in his favor and I suspect he'll ratchet up his skills with more post TJS innings under his belt. Specifically, control and command come back after velocity, so I anticipate fewer walks as the season progresses.

Be sure to check out what the rest of the Touts have to say. The piece should be posted early next week.