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Justus Sheffield Deserves Your AL ROY Consideration

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You’re probably already considering Kyle Lewis

MLB: Colorado Rockies at Seattle Mariners Joe Nicholson-USA TODAY Sports

Over at Pitcher List, I’ve just posted an article stating the case for Shane Bieber as AL MVP. As is pretty well known, pitchers almost never win MVP awards, but something that is slightly more common is pitchers that win Rookie of the Year. The Mariners have themselves an AL ROY candidate in Kyle Lewis, but I’m not convinced that Justus Sheffield should be left out of the conversation. In fact, there’s an argument to be made that he’s more deserving.

Again, I’ll note that the award inherently leans towards hitters, and so Sheffield is already starting from a deficit. Currently, Sheffield has faced 232 batters, while Lewis has faced 242 pitchers. That leans ever so slightly in Lewis’ favor, but it’s certainly close enough for comparison.

Before we get to the numbers, it should be considered that Lewis has leaned on the flashier approach of the two. He’s made plays like this Griffey-esque catch in the haze several times:

As well as plays like this at the plate:

You can see why he’s gotten so much attention this year. He was already the favorite during the preseason, but he’s probably been even better than we had all anticipated. Before I get ahead of myself and this turns out to be a Kyle Lewis AL ROY article, we’ll begin to give Sheffield the flowers that he so deserves.

This is perhaps the most significant reason Sheffield hasn’t garnered as much hype as Lewis:

So plain! So simple. So unsexy! But so, so very effective. Sheffield switched his four-seam fastball out for a sinker this year and has started to throw his changeup and slider in the zone more. That bodes for an approach that skews much more towards pitching to contact than last year, but it’s worked well for Sheffield this year. The walks are down, his WHIP and BABIP have regressed towards more palatable territories, and he’s been extremely stingy when it comes to allowing home runs. That may speak to some overperformance and future regression. This is part of the reason his FIP is so low, and is perhaps the strongest argument against Sheffield as our AL ROY.

I think there’s still a lot of room for improvement, but Sheffield has been much improved from last year. Here’s how Sheffield has compared to himself since last year:

Sheffield, 2019 Versus 2020

ERA- FIP- xFIP- SIERA
ERA- FIP- xFIP- SIERA
2019 124 105 102 4.77
2020 88 70 93 4.36

Compared to the 2019 version of himself, Sheffield has improved pretty considerably, by these numbers. Before, his overall output was something like a slightly below-average pitcher, whereas he looks more along the lines of a slightly above-average pitcher this year.

But he hasn’t only improved relative to himself. He’s been the best rookie pitcher in the AL this year too, even if there hasn’t been an overwhelming amount of competition. Consider the AL leaders in WAR:

AL Rookie WAR Leaders

WAR
WAR
Kyle Lewis 1.7
Justus Sheffield 1.5
Willi Castro 1.4
Luis Robert 1.4
Sean Murphy 1.3

You’ll see that there’s just a small space between Lewis and Sheffield. Additionally, you may also notice that Sheffield is the lone pitcher on this list. The next-best pitcher is a reliever, James Karinchak, who checks in with a 1.0 WAR.

Depending on your level on confidence in WAR, the conversation may be over there: just give Lewis the award! For me, though, it’s very much not. WAR already has error bars on either side as is, but in a 60-game season, our error bars are even wider. Other factors should always be considered, but even more so now, given the minute 0.2 WAR that separates Lewis and Sheffield. And so, we’ll consider those factors!

The cheapest way to go about this is to look at WAR, WPA/LI, and REW. The rationale here is that WAR is a counting stat the captures a player’s total contributions to their team. WPA/LI and REW also do this, but from a different angle. For our purposes, WPA/LI is superior to WPA, given that it allows fairer comparisons to be made between players, given that it’s more context-neutral (as well as a counting stat like WAR). In short, it’s WAR, but for win expectancy. REW is RE24 converted to a wins scale. It’s similar to WPA/LI, in that it’s similarly context-neutral. It also except it doesn’t take into account the inning or score of the game. As a trio, these should capture each player’s contributions to their teams. Thanks for bearing with me! Let’s look at some bar graphs.

You may prefer Lewis because he holds the lead by WAR. Willi Castro does well in each of the three categories, but doesn’t set himself apart in any of them. Even as recently as a few days ago, Sheffield may not have made the most compelling case, but it should be clear that — at the very least— he makes a case for AL ROY. That’s pretty wild, given that Sheffield hasn’t even really been mentioned as a candidate in general.

This is perhaps even more apparent in stacking the bar graph:

stacks on stacks on stacks

As I’ve said, the error bars are wide enough that we can probably consider Lewis, Sheffield, or even Castro as our AL ROY. That Lewis put up his numbers over a full shortened season (how oxymoronic!) should put an end to any support for Castro, who will end up playing short of 40 games this year. And so, for me, that leaves Lewis and Sheffield.

The last case that I’ll make for Sheffield is that he’s been pretty steady throughout the year, while Lewis got off to a blazing start before struggling pretty mightily in September.

Sheffield’s two-game rolling WAR:

Lewis’ 12-game rolling WAR:

Sheffield has been steadily building his case throughout the year, while Lewis has staggered quite a bit as of late. Coming into September, Lewis already had accumulated 1.8 WAR — a number that led all AL hitters —while Sheffield checked in at 0.9 WAR. That’s not a criticism of Lewis. It’s difficult to maintain how he was pacing through August! Rather, it speaks to how consistent Sheffield has been, and how strong he finished the year.

In the end, I think I’ve formulated a compelling argument here. Perhaps even more than I thought I would have thought when I began. It will almost assuredly resonate with very few people, but it pleases me to see the Mariners with two players who should be the two leading candidates for AL ROY.

Sheffield has lacked the swing-and-miss stuff this year to match Lewis’ dingers and home run robberies, and that may be what puts the nail in the coffin of his case for the AL ROY. But, if you’re like me, you’ll consider Sheffield a strong alternative to the case of Lewis, who will almost surely win the award. Regardless of the winner, the Mariners have to be happy with a strong year out of both of their rookies. I’ve presented the numbers. I’ll leave you to come to your own conclusion.