Finding Reasons to Doubt Luke Weaver

More often than not, I write to hype a player who has wowed me in one way or another. Sometimes, I have to put a damper on things. Through 20 National Fantasy Baseball Championship (NFBC) drafts, Luke Weaver’s average draft position (ADP) stands at a pearly 111th overall and 28th among starting pitchers.

Weaver’s 36-inning debut freaked me out a bit. It was evident he could capably prevent baserunners, or, through 20% of a season, he could at least fake it. His 3.34 xFIP suggested as much, even in spite of his abhorrent 31% ground ball rate (GB%). Everything else stunk — all the luck metrics broke the wrong way in a small sample — but it was enough to suggest a bright future for the former 1st-rounder was imminent.

I planned to avoid Weaver at all costs in 2017 because of his fly ball tendencies exclusively; I simply did not want to suffer the wrath of a juiced ball because some small-sample strikeout-to-walk ratio (K/BB) goodness seduced me. Turns out, batted ball metrics can also feel the wrath of randomness in small samples, as his ground ball rate spiked to an above-average 50%. Some of the luck metrics tempered a bit, and the result was a 29% strikeout rate (K%) and defense-independent metrics that suggested he should nearly have a flat 3.00 ERA. It’s almost like there’s a reason why this 24-year-old kid was drafted in the 1st round or something.

I’m here to pump the brakes. I’m not sold on Weaver’s peripherals. I’m willing to let you convince me otherwise, but allow me to explain.

Through almost 100 innings, Weaver’s swinging strike rate (SwStr%) stands at a paltry 9.7%, a few ticks below league-average. Yet his strikeout rate sits well above average. This is where I could probably end my argument. Strikeout and swinging strike rates are highly, highly correlated — an adjusted r2 of 0.725 — so whatever explains the remaining variance in Weaver’s gaudy strikeout rate, it better explain the heck out of it.

Again, I’m willing to concede here. Perhaps, in this instance, Weaver’s strikeout rate leads his swinging strike rate. In other words, his deficient swinging strike rate will catch up to his decidedly sufficient strikeout rate. I’m having a hard time, however, believing the individual events (pitches) that comprise an outcome (plate appearance) are the effect rather than the cause. I’m having a hard time believing that whiffs, when scattered throughout various sequences of pitches, likely at random, is less reliable than the strikeout that results from said random sequencing. (To be clear, the pitch selection is not random, but, to an extent, the outcomes are. When I say “random,” I only mean the pitcher lacks autonomy. If pitchers had full control over outcomes, there’d be no reason to play baseball.) I’m having a hard time suspending my disbelief.

Let’s assume, instead, that Weaver sustains a roughly 10% swinging strike rate through his next 200-or-so innings. I looked at pitchers who, in the last five years, recorded 300-plus innings at a swinging strike rate between 9.7% and 10.3%. The mean and median strikeout rates for these 25 pitchers: 21.3% and 20.8%, respectively. Not entirely promising, and also not entirely surprising. However, the range of outcomes — from 17.9% (Jeremy Hellickson) to Aaron Nola (25.0%) — suggest hope for Weaver he can overachieve his peripherals. Then again, there’s a chance he underachieves his peripherals — that’s variance for you — but even I admit he’s probably closer to Nola than he is Hellickson.

These comparisons alone, though, already prime Weaver for regression. If we gift him Nola’s 25% strikeout rate, which I think is very generous, he’s, well, he’s still an ace. He’d just be Nola’s clone, straight up. Yet of the concessions I’m willing to make, saying Weaver is already Nola’s equal is not one of them. Nola is really unique; his ability to coerce called strikes is nearly unrivaled among his colleagues. Weaver doesn’t have that same skill set. He’s not in the zone as much, doesn’t get as many first-pitch strikes. He’s in control, but not in as much control. We should chip away at the upper bound of the range of Weaver’s K-rate possibilities a little more.

What really concerns me, ultimately, is Weaver’s lack of effectiveness outside the zone. Those 25 pitchers with comparable whiff rates I mentioned earlier? They all have/had better chase rates (O-Swing%), and all but one have/had better contact rates on chased pitches (O-Contact%). Put into a different context: none of these 25 pitchers — with lukewarm whiff rates, mind you — rely so heavily on earning strikes on pitches in the zone.

I have yet to convince myself whether that’s a blessing or a curse. He’s not a generational talent with an overpowering fastball. It lives mostly 93, although it can touch 97 mph, but it’s not unhittable. If Weaver cultivates his success in the strike zone, then he cultivates his failure there, too. Batting average on balls in play (BABIP) and home run-to-fly ball ratio (HR/FB) exhibit weak relationships with just about any pitcher metric, yet it stands to reason Weaver’s reliance on in-zone effectiveness may contribute to his currently woeful .355 BABIP and 18.4% HR/FB through nearly 100 innings.

The baseball gods work in mysterious ways. The pendulum swings back and forth, and player performance ebbs and flows. (Just ask Robbie Ray.) Accordingly, Weaver’s BABIP and HR/FB issues may not only dissipate but also invert in 2018, thereby turning me into a laughing stock. That’s fine. It happens. (Frequently.) But if I truly place my faith in the baseball gods, and I do, then I must believe the strikeout rate regresses. I think a best-case scenario looks something like a 24% strikeout rate, 6% walk rate and 50% ground ball rate — a powered-up Gerrit Cole. That’s good. Something like top-50-overall-upside good. Steamer’s almost there minus a few ticks to the grounders and an additional tick to the walks. That prices him right-around break-even.

But I see a more likely mediocre-case scenario in which Weaver produces something like a 21% strikeout rate, 8% walk rate, and a 42% ground ball rate (his MLB career rate thus far, and much closer to his Minor League rates) — somewhere floating nebulously among Marco Estrada, Dylan Bundy, Patrick Corbin, and Tanner Roark, all being drafted 188th or later. Or a Mike Fiers without a home run problem. Except maybe Weaver does have a home run problem, which would just mean he’s a Fiers clone. That’s a far cry from a Nola clone. But I don’t think he does (yet). He did a fantastic job of limiting home runs in the minors, which I’ll give him time to prove is a repeatable skill.

None of this is to say Weaver can’t or won’t be good. He’s a mortal lock to be a top-60 starting pitcher, aka usable all year in all formats. But I’m doing my best not to be enamored by what might be illusory upside. Seems to me he’s being drafted closer to his ceiling than anything else. By October, I may be the one walking back all of this. If so, though, I imagine it will be because something else changed — i.e., he achieved true whiff rate gains by improving his offerings — and not because he retained his status-quo skills level.

So, that’s where I’m at. It appears to me a lot of the industry is pretty gung-ho about this guy, so I don’t expect to change many minds, but maybe I’m mischaracterizing everything, too. For me, he’ll be an easy fade; I’d rather have Masahiro Tanaka (105th), Jon Lester (126th), or Zack Godley (132nd) at this juncture of a draft.

Currently investigating the relationship between pitcher effectiveness and beard density. Two-time FSWA award winner, including 2018 Baseball Writer of the Year, and 8-time award finalist. Featured in Lindy's magazine (2018, 2019), Rotowire magazine (2021), and Baseball Prospectus (2022). Tout Wars competitor. Biased toward a nicely rolled baseball pant.

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Mike Dmember
4 years ago

This is not meant as a straight comparative but note the career evolution of Kershaw’s swinging strike rate:

2008: 8.7%
2009-2013: 10.0-11.4%
2014-2017: 14.1-15.9%

Baller McCheesemember
4 years ago
Reply to  Mike D

SOURCE CONFIRMED: Luke Weaver is the next Kershaw.

4 years ago

Does this by correlation mean Mike Fiers IS Kershaw right now?

Mike Dmember
4 years ago

Correct it wasn’t to show Weaver = Kershaw. More to point out some pitchers go through change in that stat. It did for Sale and Scherzer as well.
4 years ago
Reply to  Mike D

Weaver’s high k rate is because of his curve ball. what is the % on his curveballs? must be high.

4 years ago

yeah, the curve is loopy and just a show-me pitch. he’s succeeded by commanding his fastball and change really well, and being deceptive.

worth noting that he always ran very high IFFB% in the minors. didn’t carry over to the majors, but if/when it does that mitigates a lot of the HR/FB concern for me.

4 years ago

Interesting, never knew that — thanks!

4 years ago
Reply to  aschrag83

FWIW, Eno recently put out an article about Wainwright with a quote from Weaver on how Wainwright has been helping him develop the curveball as more of a weapon, less of a “show-me” pitch.

4 years ago
Reply to  Mike D

Kershaw also added one of the best sliders in the game in that period