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Weaver the Reliever? I’m a Believer

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Fresh off a demotion to the bullpen, how will Luke Weaver fare as a reliever?

Photo by Dilip Vishwanat/Getty Images

I think it would be fair to say that the writers for this website are high on Luke Weaver. Whether it’s Lance Brozdowski’s multiple analytical posts on Weaver’s pitch mix and changeup or my paean to Weaver’s effectiveness and optimistic trade valuation, we probably see him more favorably than a random cross-section of Cardinals fans. Bearing that in mind, I still can’t give up my view that Weaver is a great major league pitcher, even if the results haven’t quite been there (understatement alert) this year. Now that he’s been banished to the pen, I’ve shelved my dreams of discovering the next Aaron Nola for the year, but now I’m on to thinking of him as a multiple-inning destroyer in the Andrew Miller mold. Why would Weaver go from scuffling starter to unhittable reliever? Let’s go to the tape.

The first thing to look at is how Weaver’s game has been his first time through the order. That, after all, is what he’ll be facing as a reliever unless Mike Shildt goes really crazy. Weaver has pitched roughly 100 innings the first time through the order in his career and roughly 85 the second time through. Let’s take a gander at some relevant splits, shall we?

Luke Weaver, 1st and 2nd Time Through Order

Times Through 1st Time 2nd Time
Times Through 1st Time 2nd Time
K% 25.7% 23.2%
BB% 6.6% 7.0%
HR/9 0.72 1.67
ERA 3.35 4.87
FIP 2.93 4.6
wOBA 0.298 0.332

Okay, so literally every number is better the first time through the order. Good news! That shouldn’t be too surprising, though, as the times through the order penalty is pretty much baseball orthodoxy at this point. Pitchers get worse the more times they go through the order, we get it. Let’s see what the major league numbers look like on the year, and how those compare to Weaver’s changes:

Statistical Change, 2nd vs 1st Time Through Order

Statistic MLB Change Weaver Change
Statistic MLB Change Weaver Change
K% -2.60% -2.50%
BB% 0.20% 0.35%
HR/9 0.1 0.95
ERA 0.3 1.51
FIP 0.63 1.67
wOBA 0.01 0.033

Well, the first thing to notice here is that Weaver has been more impacted by the times through the order penalty than your average major league pitcher. It’s been in a pretty specific way, too; his strikeout and walk numbers decline very similarly to the major league average. The real killer in his numbers is the spike in home run rate- Weaver basically gives up an extra home run per nine innings the second time he faces a lineup. You don’t need to be a sabermetrician to know that that’s bad.

It would be easy to say that the solution is obvious. Just make Weaver pitch through an order only once, and it’s all solved. There’s a slight problem with this, however. It’s incredibly unlikely that Weaver’s true talent home run rate is 2% the first time through the order and 4% the second time through. He’s only given up 31 home runs in his entire career- we’re necessarily dealing with very small samples here. We need to regress this to the league average somewhat. Now, what follows here is some bad science. I don’t have an exact formula for how to regress someone’s times through the order home run split back towards average. What I’m going to do, instead, is regress both home run rates towards average and see what a resulting split might look like. To do so, we need to add 1320 league-average PA (per this article) to each and see what we end up with. This leaves us with home run rates of 2.7% the first time through the order and 3.3% the second time through. Plugging this result into FIP calculations tells us that at these regressed home run rates, Weaver’s first time through the order would look something like a 3.32 FIP/3.55 ERA career-to-date, while his second time through the order would be more like 3.7 FIP/3.95 ERA. That’s the most aggressively regressed version, so it’s probably an okay baseline for what we’d expect of Weaver’s line going forward. Even at that markedly higher home run rate, it still sounds like he would be a valuable bullpen piece, and there’s an argument to be made that I should regress both numbers less, making him look even better.

Okay, so with a little baseball and statistical alchemy, we’ve figured out what Luke Weaver might look like going forward if he only ever faced an order one time through. That version of Weaver is already a valuable pitcher- he’d be neck-and-neck with Carlos Martinez as the third guy out of the bullpen. We’re not done yet, though. The reason starters improve when sent to the bullpen isn’t exclusively because they get to skip their second and third turns through a lineup. There are two other major factors. First, without having to think about having to face the same batter multiple times, they can throw their better pitches more often without regards for consequences. Secondly, they can let their fastball eat, gaining velocity at the expense of endurance they won’t need in their brief stint. Now, it’s very hard to quantify the gains from focusing on your better pitches due to the complex relationship between pitch frequency and effectiveness, but from a qualitative standpoint it can’t be bad to take a pitcher with a good fastball, great changeup, and bad curveball and cut out the worst pitch. When it comes to increased fastball velocity, we can’t really know how that will affect Weaver’s results either. That said, adding a tick or two on his fastball certainly won’t hurt its value, and it’s already been a tremendous weapon for him in the majors. I did a quick study of pitchers who have thrown in relief and as a starter in the last two years, and it looks like they pick up between one and two mph of velocity on their fastball. I wasn’t able to quantify how much more effective the pitch was, but assuming a general improvement makes sense.

After looking through Weaver’s past results and imagining his updated arsenal as a multi-inning stopper, I only had one question left; are there actually relievers who work primarily with a fastball and changeup? Luckily, the answer is yes. Fifteen relievers with at least 30 innings pitched in 2018 use their changeup more than Weaver has this year, and the ones who also throw as hard as he does are a really interesting group. There’s multi-inning monster Chris Devenski. You’ve got effective relief arms in Fernando Rodney and Jose Leclerc. There’s even a relief-conversion success story in Adam Conley, who went from unplayably bad starter to decent reliever when he switched to the bullpen.

Of all these names, Devenski is the most interesting to me by far. He’s a symbol of a new way of managing bullpens, a multipurpose weapon who can come in at almost any point in the game to pitch an inning or two. Before this year’s injury-beleaguered campaign, he’d averaged nearly 5 outs per appearance as a reliever, and even after including this year’s numbers he records a healthy 4 and change outs per appearance. That’s the kind of pitcher you could imagine as an ideal outcome for Weaver. Armed with a lefty-devouring changeup, he could appear from the bullpen as needed to kill rallies or back struggling starters. In figuring out if that could be Weaver’s eventual destiny on the Cardinals, I decided to compare the fastballs and changeups of the two pitchers, as well as a rough guess at what Weaver’s other pitches might look like as a reliever.

First, there’s the fastball. As you might expect from a guy who wears ‘The Dragon’ on Player’s Weekend, Devenski has a four-seamer that explodes through the zone:

Look familiar? That’s a skill Weaver has already displayed. Here he is making Freddy Galvis look sluggish:

That, of course, is only the start of Devenski’s arsenal. While his fastball often sneaks up on hitters, his changeup eats them alive. While he can certainly throw a Bugs Bunny-esque change with tons of horizontal run, he prefers to take the bottom out of the pitch, as he does here to an overmatched Gary Sanchez:

Man, that’s some nice pitching. Let’s see it again in slow motion:

Okay, so that’s a hell of a pitch. Weaver also has that style of changeup in his bag of tricks, as we see here. Thanks for playing, Austin Meadows:

The quintessential Weaver changeup, however, doesn’t drop straight into the dirt. That pitch is a mindbending, stop-trying-to-hit-me-and-hit-me tesseract that makes batters wish they asked Morpheus for the blue pill. Does this type of changeup play up in relief? I have no idea, honestly. I just wanted an excuse to show a gif of it:

Again, in slow motion:

Now, looking at videos is fun, but I could have picked those highlights out to bamboozle you, to hide the fact that their pitches aren’t that similar aside from these few standouts. In actuality, though, Devenski and Weaver are pretty comparable. Devenski’s fastball is about a mile an hour faster on average, though you’d expect that gap to shrink as Weaver adds velocity in the bullpen. Both pitches are the high-spin-rate jobs that analysts love so much these days (myself included). Devenski has a bit more horizontal run to his, while Weaver’s moves a bit more vertically. Overall, the pitches are pretty indistinguishable. When it comes to changeups, Weaver throws his about a mile an hour harder on average, nothing worth writing home about. Again, Devenski throws his with a bit more horizontal movement, while Weaver’s has a bit more vertical to it. A lot of that comes down to pitch selection, though. When Weaver throws his changeup below the zone, it mirrors Devenski’s almost exactly.

There remains the sticky matter of a third pitch. Devenski has a slider he’ll occasionally use to ambush hitters who are sitting changeup. He throws it less than 20% of the time, often enough to keep people honest but rarely enough that it’s clear it’s not a pitch he’s in love with. Weaver’s curveball has been too bad to keep anyone honest, so it seems unlikely he’ll use it very often in relief. Instead, I’d like to see him go to his cutter a bit more. It has the advantage of sitting along the spectrum of velocity he’s already using (85-95mph) while breaking totally differently than either of his marquee offerings. He’s experimented with the cutter this year after completely scrapping it last year, and the early results have been positive, or at least less negative than the curveball.

Well, this article took a bit of a turn halfway through. Initially, I hoped to come up with some mathematical expectation for what we might see out of Weaver the Reliever. In the end, though, I’m pretty happy with the direction I went in comparing him to existing changeup-dominant relievers. I’m quite content to mentally bucket him as a poor man’s Chris Devenski and see whether he can actually live up to the billing. If he can’t be Devo the Dragon, maybe he can still be Weav-o the Dragon Whelp? In a lost season for Weaver, it’s at the very least encouraging to see that pitchers of his general ilk profile well in relief even if they can’t squeeze enough out of their two-pitch arsenal to dominate as starters. I still expect Weaver to tinker with his secondary pitches over the winter and return for 2019 as a starter, but a bullpen front five of Hicks, Norris, Martinez, Weaver, and Hudson sounds pretty great, particularly with Chasen Shreve on hand for lefty help. With the playoff odds needle pointing upward, an embarrassing buffet of bullpen riches is just the thing to get me excited for October.