Thread by @DownToBlack

#BlueJays ⚾️🧵Yusei Kikuchi Deep Dive

Another thread about belief in September stats, about finding comps for such a strange year & about mound position & usage.

Let's start here:

Reliever Strikeout Rate
1. Diaz 50.2%
2. Fairbanks 43.7%
3. Williams 40%
4. Kikuchi 39.8%

Now, that leaderboard is obviously tongue-in-cheek (he only has 18 IP as RP), but his performance & aggressiveness in September was really intriguing for hard-core Jays fans.

But it was such a weird year.

Check out this list of 10+ strikeouts per 9, 5+ walks per 9 (100 IP min)

Robbie Ray being on that list is interesting for a few reasons...

And the Jays did something with Kikuchi in September 2022 that they did with Robbie Ray in September 2020: They moved him on the mound towards First Base.

I noticed, literally in his first Spring start, that the Jays had moved Kikuchi to the 3B side of the mound & wondered (left) how that would impact him.

It was a drastic move (right), but again, in September, they moved him back as far towards first base as he's ever been.

Left: vs TB early in year
Right: vs TB in September

Notice the left foot position off the top, then at :09 notice how release point is nearly in middle of LH batter's box.

Left: April
Right: September

I think this is about creating tougher angles vs lefties, but also creating a better angle to work inside vs righties.

I think generally this is about creating a better way of pitching to his "glove side"

Below: September sliders

Some vs lefties, some vs righties, but all working on that "glove side"

He threw a higher rate of pitches to that side of the plate in September/October than he had in any other month of his MLB career.

Just look at the comp b/w flight of his sliders in an April game vs a September game.

You can see how substantial the move was towards First & just the path is more diagonal.

It feels subtle looking at it on a computer screen, but in batter's box, it'd be really noticeable!

So there was a legit, quantifiable mechanical change that led to improved results. That's good!

He also made drastic usage changes in September, throwing his "spin" (breaking ball, cutter/slider, whatever you want to call it) way more overall, but especially early in an AB:

This change is mitigated by the fact he faced a higher rate of lefties in September/October than he ever had, but still, even when you look at usage vs righties, there was a fundamental shift in how Kikuchi & the Jays attacked.

Here's one anecdotal way of illustrating how much more they were leaning on the slider.

He faced ten 2-0 counts in September/October & threw his breaking ball in every one of them.

Why more sliders? One theory: it makes the fastball a more effective pitch late in at-bats.

By run value, Kikuchi's fastball has been his worst-performing pitch over his career, so you could say, he's throwing his slider more in the hopes of making his fastball more effective.

Video above: Starts slider, then the only 2 fastballs he throws produce a foul back where the hitter was late & a take for a backwards K.

Next Example:
Get-me-over slider (strike 1)
Miss fastball
Good slider in
Slider in (foul)
Miss fastball
Slider in (foul)
Fastball (K)

That AB was very Robbie Ray-esque.
Get ahead for strike 1, if hitter is sitting fastball, throw him sliders in and he'll be out in front, finish with fastball. Love it.

It just seems like he can command his breaker better than his fastball.

As I said off the top, it's really hard to find people with seasons like Kikuchi's strange 2022! But I tried & maybe the closest modern example is Drew Smyly's age-30 2019.

21 starts, lefty, 6.24 ERA, 6.26 FIP, 1.59 WHIP, but 9.5 K/9...

Smyly is 18-13, 3.96 ERA since. How?

Smyly's best pitch was his breaking ball.

So he threw it more. And challenged hitters in the zone with it more.

Aren't analytics simple?

Questions ahead of 2023:

- If he returns to a starting role, can his arm withstand the heavy breaker usage he had as a reliever?

- Will he maintain his newfound aggressiveness as a starter?

- How will he incorporate his split-change?

What do I think will happen?

He'll at least start the year in the rotation, that's the best way of giving your org a chance at maximizing Kikuchi's value.

But, knowing there is a path to him being a viable option in the 'pen is a nice insurance policy.

To summarize & establish a pattern with other 🧵: Quantifiable, measurable changes in mechanics & usage led to encouraging results for Kikuchi in September & October.

That gives me some hope in Kikuchi being a contributor in 2023!

It's not much & definitely no guarantee, but:

One other way of looking at it: