Ever since Hisashi Iwakuma announced he was returning to Japan to continue his baseball career, I’ve been reflecting on his Seattle Mariners legacy. Specifically, his place among the best pitchers in franchise history.

When I told my wife (a lifelong Mariners fan) I was writing about Iwakuma’s MLB career, she paused for a moment and delivered a straightforward response. “He was a linchpin.”

Linchpin is an interesting characterization; one I hadn’t considered. Based on Iwakuma’s conventional stat line, his Mariners career looks relatively impressive: 136 starts and 14 relief appearances in 6 seasons with a 63-39 win-loss record and 3.42 ERA.

Still, my wife didn’t describe Iwakuma as “relatively impressive.” A closer look at the player affectionately referred to by fans as “Kuma” suggests something far better.

It’s Not How You Start, It’s How You…

When Iwakuma signed with the Mariners in January 2012, Geoff Baker of the Seattle Times noted concerns regarding the right-hander’s drop in velocity during the year prior to his signing. This may explain Seattle’s slow rollout of the star pitcher from Japan.

Iwakuma began 2012 in the bullpen with the Mariners using him sparingly. In fact, he was the last healthy member of the Opening Day squad to see action. Through the club’s first 54 games, Kuma appeared just five times logging 15 innings.

Despite the inauspicious beginning, Iwakuma’s rookie campaign kicked into gear once he was inserted into the rotation in July. His 2.65 ERA over the last three months of the season was tenth best among MLB starters.

This was a preview of what was to come.

The Wonder Years (2013-16)

After his debut season, Iwakuma signed a two-year extension to remain in Seattle. He promptly rewarded the team finishing third in 2013 AL Cy Young Award voting behind winner Max Scherzer and compatriot Yu Darvish.

Based on the Baseball Reference version of wins above replacement (bWAR), Iwakuma was more valuable (7.2 bWAR) than any AL pitcher in 2013. Only Clayton Kershaw (8.0) of the Dodgers proved better.

In 2015, Iwakuma made franchise history becoming the fifth Mariner to throw a no-hitter. His gem came against a Baltimore Orioles lineup with five players with an .800-plus OPS:  Manny Machado, Gerardo Parra, Adam Jones, Chris Davis, and Jonathan Schoop.

Iwakuma proved to be more than a one-year wonder or a footnote in the record book for tossing a no-no.

During the 2013-16 seasons, Kuma delivered elite-level performances on a regular basis. Here’s his combined stat line for those years and where he ranked against AL pitchers with 100-plus starts.

ERA
ERA+
WHIP
BB%
SO%
OBP
SLG
WAR
Kuma
3.43
111
1.12
4.4
20.4
.282
.400
14.8
AL Rnk
7
11
3
2
15
7
17
6

Iwakuma’s 14.8 bWAR finished ahead of Cy Young Award winners Justin Verlander (14.7), Dallas Keuchel (11.8), and Rick Porcello (11.3). He also held opposing hitters to a .282 OBP, slightly better than two others with Cy Young hardware – Corey Kluber (.284) and teammate Felix Hernandez (.286).

As an aside, I always perceived Iwakuma having a knack for avoiding the long ball with men on base. Turns out the numbers say I was onto something.

A comparison of Kuma’s best season (2013) to other starters receiving Cy Young votes that year shows he was better at preventing damaging dingers.

HR MOB
Total HR Allowed
HR% MOB
Hisashi Iwakuma
6
25
24%
Yu Darvish
9
28
32.1%
Max Scherzer
6
18
33.3%
Anibal Sanchez
3
9
33.3%
Matt Moore
5
14
35.7%
James Shields
8
20
40%
Chris Sale
10
23
43.5%
Felix Hernandez
7
15
46.7%
Bartolo Colon
7
14
50%

For those wondering how Iwakuma did during his entire career, he allowed 115 homers with 32 coming with men on. That’s a 27.8% rate and relatively close to his 2013 excellence.

Injury Report

It is true Iwakuma suffered his share of injuries. A strained tendon in his right middle finger delayed the beginning of his 2014 season. He then missed over two months with a lat strain the following year. Still, Kuma was available more often than some may suggest.

Despite the setbacks just mentioned, Iwakuma made 114 starts during 2013-16 making him one of only 16 AL pitchers to make 100-plus starts.

When the Mariners re-signed Iwakuma in December 2015, the Mariners seemingly had a glut of starting pitching with Hernandez, newcomers Wade Miley and Nate Karns, plus holdovers James Paxton, Taijuan Walker, and Mike Montgomery. Ironically, only one pitcher made 30-plus starts that year – Kuma.

In 2016, Iwakuma made 33 starts logging 199 innings, but appeared worn down by season’s end. In September, he had a 4.64 ERA with opponents hitting .320 against him during six crucial starts as the Mariners were trying to remain in the Wild Card race.

This too was a preview of what was to come.

All Good Things

It turns out 2016 was Iwakuma’s last good season. The following Spring Training, there were whispers of declining fastball velocity after he surrendered 8 runs and 16 hits during 12 Cactus League innings. On the other hand, a veteran struggling to get on track in March normally means nothing.

Unfortunately, it did.

After two respectable six-inning outings to begin the season, Kuma quickly regressed. In his next four starts, he averaged just 4.8 innings with a 5.68 ERA. And those concerns regarding his Spring Training velocity?

Unlike in 2012, they were well founded this time.

Never known as a hard-thrower, Iwakuma’s velocity reached an alarmingly low level. Here’s an illustration of his average fastball speed during his MLB career.

In May, Iwakuma went to the DL with shoulder inflammation and never pitched for the Mariners again. He’d continue attempting to return until deciding to return to Japan.

Kums’s last appearance on the Safeco Field mound was throwing a ceremonial first pitch to countryman Ichiro Suzuki this past September.

Historically Speaking

Obviously, Iwakuma was an important fixture with the Mariners. But how does he compare to the all-time best pitchers in franchise history?

Better than “relatively impressive.”

The following illustrates Iwakuma’s career stats and his ranking among Mariner pitchers with 500-plus innings. He stacks up well against some of the most famous names in franchise history.

ERA
ERA+
WHIP
BB%
SO%
OBP
SLG
WAR
Kuma
3.42
112
1.14
5.2
20
.282
.403
17.3
M's Rnk
2
5
1
1
5
1
9
7

Earned run average may not impress seamheads. However, it’s still worth noting Iwakuma’s 3.42 ERA ties for second best in Mariners history with Randy Johnson and former teammate Paxton.

Kuma’s league and park adjusted earned run average (ERA+) was equally impressive. He’s in a fifth-place tie with Floyd Bannister and Mariners Hall of Fame inductee Jamie Moyer. Only Johnson, Hernandez, Paxton, and Freddy Garcia are better.

Although never considered a strikeout pitcher, Iwakuma’s 20% strikeout rate is only outdone by four hurlers known for routinely missing bats – Johnson (28%), Paxton (25.7%), Hernandez (22.5%), and Mark Langston (21%).

Clearly, the stats say Iwakuma merits inclusion in any discussion regarding the best pitchers in franchise history. As a bonus, he managed to contain a notorious Mariner-killer.

Iwakuma faced Mike Trout more times than any hitter during his MLB career and owned the future Hall of Famer. In 61 plate appearances, Trout had just a pair of home runs and a .189/.279/.302 slash against Kuma.

Jack’s Best Pickup?

Ask a Mariners fan to name the best free agent acquisition by former general manager Jack Zduriencik and most likely say Nelson Cruz. That’s reasonable, although there’s an alternative to consider – Iwakuma.

I’m not saying Iwakuma was better than Cruz. After all, Boomstick was an everyday player and did hit more home runs (163) than any other major leaguer during his four-year stint with Seattle. But Kuma’s bWAR suggests he delivered similar value.

In six seasons with the Mariners, Iwakuma tallied 17.2 bWAR with Cruz at 16.8 bWAR. Granted, Boomstick played just four years in the Emerald City. However, the worth of these two superb players was more comparable than some might expect.

Then there’s the matter of salaries.

Four years of Cruz cost the Mariners $57 million, a relative bargain based on today’s market. Then again, Iwakuma cost even less ($47.6 million) for a longer period. Plus we’ve already demonstrated he compares favorably with some of the best arms in franchise history.

Whether Iwakuma was actually more valuable than Cruz is debatable, but the gap between the two is much smaller than some may realize. Jack Z deserves credit for acquiring both Kuma and Boomstick. Each exceeded expectations at a relatively low cost.

Finally

Hisashi Iwakuma wasn’t the Mariners’ best starting pitcher, but he solidified and elevated their rotation. His accomplishments include being a Cy Young finalist and top-10 pitcher and throwing a no-hitter. 

Whether he belongs in the Mariners Hall of Fame is something for fans to debate and the ownership group to ponder. But it’s clear Kuma was a positive influence on the organization and beloved by fans.

Sounds like a linchpin to me.

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Luke Arkins

Luke is a native New Yorker, who grew up a Mets fan. After the US Navy moved him to the Pacific Northwest in 2009, he decided to make Seattle his home. In 2014, Luke joined the Prospect Insider team and is now a contributor at HERO Sports also. During baseball season, he can be often found observing the local team at Safeco Field. You can follow Luke on Twitter @luke_arkins

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