Getting to Know Yamamoto, Imanaga, Matsui, and Other NPB Pitchers New to MLB

March 25, 2024

Matt breaks down key recent Nippon Professional Baseball (NPB) pitchers who will transition to MLB in 2024 or later from the perspective of outcomes analysis.

Perhaps never before have so many pitchers made the leap from Nippon Professional Baseball (NPB) to MLB as this offseason.

Yoshinobu Yamamoto (now with Los Angeles Dodgers) and Shota Imanaga (now with Chicago Cubs) were the big fish, but they were hardly alone as MLB clubs in general seem increasingly eager to sign foreign league hurlers.

The purpose of this article is to gain some familiarity with these first-time 2024 MLBers and 2024 MLB returnees by examining their recent history of fundamentals-rooted pitching outcomes as quantified by the FaBIO model.

Brief Explanation of the FaBIO Model

My Fielding- and Ballpark-Independent Outcomes (FaBIO) pitcher evaluation model sorts every plate appearance into one of 12 outcome bins (BB+HBP, K, IFFB, Pull-Third OFFB, Center-Third OFFB, Oppo-Third OFFB, Pull-Third LD, Center-Third LD, Oppo-Third LD, Pull-Third GB, Center-Third GB, Oppo-Third GB) and credits the pitcher with their league's mean runs value for said particular event that season. The most runs-punitive events for pitchers are Pull-Third OFFB, the three line-drive types, and BB+HBP. The most runs-preventing events for pitchers are K, IFFB, and Pull-Third GB.

Dividing their total number of expected runs by batters faced (BF) yields expected runs per batter that can be percentile ranked relative to the league mean and standard deviation for that parameter amongst league qualifier starters (else relievers) to arrive at their Overall Rating.

Its three subcomponents of Control Rating (CTL, based on BB+HBP per BF), Strikeout Rating (K, based on K per BF), and Batted Ball Profile Rating (expected runs per batted ball) are also reported to understand better the path the pitcher traveled to reach their Overall (reverse engineering Overall reveals that expected run avoidance is generally 44% Strikeouts, 34% Batted Ball Profile, and 22% Control).

To better understand the path to Batted Ball Profile, we will also examine percentile ratings for select batted ball event types (on a per batted ball basis). Lastly, to check how well expected batted ball outcomes matched real-world ones, we will compute percentile ratings for the avoidance of hits (AVG) and isolated power (ISO, or simply extra bases) on batted balls (recognizing full well that these two parameters are neither fielding- nor ballpark-independent outcomes).

A percentile rating of 97 amounts to plus-plus (two standard deviations above the mean), 84 is plus (one standard deviation above the mean), 69 is half plus, 50 is average, 31 is half minus, 16 is minus, and three is minus-minus.

Pitcher Evaluations

Yoshinobu Yamamoto - RHSP, Los Angeles Dodgers

Yamamoto prominently features a splitter that he typically sets up with lowerly-located four-seam fastballs. Owing to that approach bias he induces more grounders than four-seam-tossers typically do but at the expense of relatively more line drives (and singles, as an offshoot) per batted ball than that degree of ground baller usually allows. But beyond that line drive and hit vulnerability there are not many defects in the FaBIO profile as else he is relatively averse to BB+HBP and OFFB+Pull OFFB+ISO on batted balls.

A downward trend in GB can be spotted from 2022 NPB to 2023 NPB to 2024 MLB Spring Training and if that carries over to the 2024 regular season the LD and hit avoidances should improve but at the expense of losses in OFFB, Pull OFFB, and ISO avoidance. In NPB, batter-handedness splits have leaned slightly in the forward direction (Same-Handed Batters Overall > Oppo-Handed Batters Overall). In throwing a cutter and curve rather than a slider/sweeper there is some suspicion that the MLB splits may skew in the reverse direction and more widely, and his 2024 MLB Spring Training (through March 19) FaBIO line lends some credence to that forecast.

Kevin Gausman makes for a logical MLB SP comp as a splitter-heavy RHSP who lands K aplenty but with higher LD/singles risk around fewer BB+HBP and relatively few OFFB+Pull OFFB. If not during a teeth-cutting 2024 MLB season then at least by 2025 Yamamoto should have a leg up Gausman with relatively more GB keeping LD Avoid from sinking too low while boosting OFFB & Pull OFFB Avoids enough to lessen extra bases risk. Yamamoto need not look too far in search of another similar RHSP, as rookie teammate Gavin Stone has flashed a similar mix of (pitches and) outcomes in his 2023 AAA & 2024 MLB spring (but not 2023 MLB debut) FaBIO lines.

Fastball-arsenal-related issues in the batted ball profile are somewhat to be expected with a pitcher who throws a splitter or changeup as often as this duo does. For one, there would be no reason to throw that trick change of pace offering so much if their fastball arsenal outcomes were rock-solid. How do you think they got to be that way?

Expect some March through May hiccups as Yamamoto adjusts to MLB batters who skew more physical and swing-aggressive relative to NPB ones. We might see more walks than forecast and perhaps also more aerial pulls and ISO if he throws the splitter too much into the down-and-in quadrant of RHB. Dynasty league owners are advised to ride out any early struggles. Nonowners should explore acquiring him if the trade returns drop to a reasonable level.

Shota Imanaga - LHSP, Chicago Cubs

Flyballing lefthanded starters were the subject of only my second RotoBaller article two springs ago and Imanaga fits that description to a tee and then some. For this variety of lefty (or righty) starter to thrive, they must generate many IFFB (which have roughly the same runs value as K) and limit BB+HBP and LD traffic on the basepaths ahead of their OFFB so as to keep the runs consequences of their many OFFB to a minimum (in an era in which it is relatively easy for so many major leaguers to go deep). The first 41 batters of his MLB Spring Training game work confirms that Imanaga accomplishes the first two objectives by getting tons of IFFB and being stingy with BB+HBP but skews subpar at LD Avoid.

The 2023 NPB batted ball outcomes were poor, as he rated 34th percentile at avoiding hits (AVG) on batted balls and 7th percentile at avoiding extra bases (ISO) on them. Neither outcome then was overly surprising subpar LD Avoid, OFFB Avoid, & Pull OFFB Avoid Ratings. This spring we have seen more of the same CTL+K+IFFB versus LD+OFFB+Pull OFFB tightrope act, so Imanaga seems unlikelier to alter his approach any time soon. The 2024 MLB mystery will be if Imanaga's high walk avoidance proves a blessing that limits the runs penalties of his rather many OFFB+Pull OFFB or instead a curse that springs from misguidedly forcing too many drivable and slug-able pitches into higher-risk locations of the strike zone.

As concluded in the companion articles from the 2022 preseason, expect this type of flyball-extreme pitcher to experience peaks and valleys from start to start, month to month, and year to year. His 2022 NPB FaBIO line probably represents a best-case scenario for a future MLB season in which the CTL+LD Avoid+Pull OFFB Avoid stars align about as well as they could for this style of hurler. Owing to the forecast volatility in batted ball outcomes, redraft fantasy league players would be advised to adopt a "buy low, sell high" mentality with Imanaga. Dynasty owners may simply opt to ride out the highs and duck the lows with occasional stints off the active roster.

Yuki Matsui - LHRP, San Diego Padres

Among a series of cost-saving offseason moves, Padres rather willingly let their late 2022 through 2023 lefty closer Josh Hader walk as a free agent and signed little lefty NPB closer Matsui to a five-year contract that pays him a mere $28 million total ($5.6M/year). The transaction was completed some 30 days before Hader officially signed with the Astros for $19M annually over five guaranteed years.

In the realm of FaBIO fundamentals, Matsui profiles as a K specialist who rates above average to better at both CTL and Batted Ball Profile. Over a smaller 11-batter sample of MLB Spring Training game work through March 19, not much seems to have changed relative to recent NPB campaigns with Matsui again posting a plus plus 98 Overall Rating.

Given that Matsui came up shorter at both IFFB & LD Avoid in 2023 NPB while sporting 17 GB & 19 OFFB Avoid Ratings, the preferred plan of fastball attack would skew lower to yield more neutral GB & OFFB Avoid Ratings like the line of 2022 NPB. That Matsui biased his OFFB contact rather late (Pull OFFB Avoid >> OFFB Avoid) in NPB is a positive though he has yet to parlay that outcome into better ISO (extra bases) avoidance on batted balls. Matsui has and should continue to sport mild reverse batter handedness splits, which has him best cast as an all-comers LHRP as opposed to one who would be summoned to enter a game to face a lefty batter.

Coupling 2021-2023 NPB closing success and shortness-and-arsenal-assisted novelty to MLB batters with newly anointed closer Robert Suarez's uninspiring FaBIO fundamentals over the past two seasons (since also emigrating from NPB as one of its top closers after five seasons there), Matsui makes for a strategic fantasy pickup who could easily log 12 to 24 saves in 2024 MLB beyond a dozen to more holds. Pitching mostly in San Diego and a fair amount in Los Angeles and San Francisco would also stand to limit the relative potential of OFFB to become extra-base events some more.

Over the next five years, would you rather pay 28-year-old Matsui $28 million or 30-year-old Hader $95 million? Or pay 33-year-old Robert Suarez $20 million over the next two years (which could become $36 million over the next four should he exercise a pair of one-way player contract options)?

Other NPB Pitchers Who May Appear in 2024

The most famous of them would have to be Kodai Senga, who translated stronger 2022 NPB FaBIO out-generation fundamentals exceptionally well to 2023 MLB with the Mets before shoulder trouble wiped out his 2024 spring. Ex-MLBers Scott McGough and Colin Rea also re-transitioned into MLBers during 2023 after stints in NPB. All three project as above-average fantasy-league-rosterable pitchers in 2024.

Former Blue Jays MLB RHP Jacob Waguespack inked a minors deal with Rays after two somewhat successful NPB RP campaigns and was selected to the MLB roster this spring; though he seems best cast as a R-on-L RP per recent FaBIO Ratings, Rays are using him as a length option. Veteran NPB mid-rotation starter Naoyuki Uwasawa also signed a minor league deal with Rays but his spring Overall barely tops minus minus.

With the exception of not landing K over 34 MLB batters with the Yankees a year ago, the K and Batted Ball Profile out-generation fundamentals of Colten Brewer have been outstanding since the start of 2023. A 100 Overall earned this spring has him destined to be added to the Cubs roster this April or May for another go at MLB batters.

After middling success as an SP in the prior two NPB seasons, Cuban Yariel Rodriguez broke out as a 2022 NPB short RP but never reported to his NPB club after a spring 2023 stint with the Cuba World Baseball Classic squad. Blue Jays inked Rodriguez to a five-year $32M contract that included one option year that is being used now to ramp him back up to speed after just a pair of MLB Spring starts sandwiched around a back-spasms-owed sabbatical. Jays seem intent on stretching Rodriguez out as a starter, but he likely tops out as a league-average SP who would have a much greater impact in a short RP role that mirrors his 2022 NPB usage.

On the Horizon: Pitchers of Interest Still in NPB

The best and most fundamentally-rounded pro starting pitcher in Japan for two seasons running hasn't been perennial NPB top-pitcher-award-winner Yamamoto but rather three-years-younger RHSP Roki Sasaki, who just completed his third NPB campaign. The winter scuttlebutt was that owing to years ago securing consent from his NPB signing club to jump to MLB sooner than customary, he will come stateside next offseason even with international free agency signing bonus restrictions in place (owing to his youth). Sasaki has topped the NPB SP Overall charts in each of the last two seasons and with Overall Ratings that only Jacob deGrom has (twice) beaten in MLB over the same timeframe.

The full 2023 NPB SP Qualifier leaderboard is sorted out as follows, with Yamamoto ranking 3rd in Overall Rating and Imanaga 4th.

Rookie RHSPs #2 Shoki Murakami and #7 Shunpeita Yamashita impressively landed here and should already be squarely on the radar of MLB clubs. At 25 years of age (like Yamamoto), the undersized (a few ticks smaller than Yamamoto) Murakami is free of international free-agent restrictions should he perform well enough ahead to be posted. The 6'2" Yamashita is not yet 22, so he is unlikelier to enter the NPB to MLB transfer portal for a few more years. If ex-MiLBer/MLBer Foster Griffin posts a second plus Overall full season in two tries in 2024 NPB, he likely commands a major league contract next winter as a "some K, some GB" sort of LHSP.

The 2023 NPB RP leaderboard was topped by a pair of Cubans who have been in NPB since 2017. Citizenship-related immigration hurdles would have to be cleared but else Livan Moinelo and Raidel Martinez would be candidates to receive a major league contract from an MLB club. Not so much the still-excellent Roberto Osuna, who likely has multiple domestic abuse transgressions documented in his league office files.

Yuki Matsumoto may draw some MLB club interest as a right-on-right-leaning K+IFFB specialist. The top out-generators among Japanese RP would be younger yet wilder RHRPs Shinya Matsuyama and Yuki Udagawa, whose stout batted ball profiles and strikeouts make their walks that much less runs-punitive relative to the typical NPB reliever.

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