Arizona Diamondbacks: How Yoshihisa Hirano Became Key Part Of Relief Corps

PHOENIX, AZ - JUNE 14: Relief pitcher Yoshihisa Hirano #66 of the Arizona Diamondbacks prepares to pitch against the New York Mets during the seventh inning of the MLB game at Chase Field on June 14, 2018 in Phoenix, Arizona. (Photo by Christian Petersen/Getty Images)
PHOENIX, AZ - JUNE 14: Relief pitcher Yoshihisa Hirano #66 of the Arizona Diamondbacks prepares to pitch against the New York Mets during the seventh inning of the MLB game at Chase Field on June 14, 2018 in Phoenix, Arizona. (Photo by Christian Petersen/Getty Images) /
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The Arizona Diamondbacks have the best bullpen in baseball. At least, the argument can be made that they do. One key element of their successful relief corps has been an under-the-radar offseason signing.

In a year where there has been some inconsistency, both in health and performance, the bullpen has been a rock for Arizona. Their relievers lead the league in ERA, with a 2.58 mark and are third in WHIP, at 1.13. They don’t strike out a ton of hitters, but rely on contact in front of a really good defense. The fact that they’re sixth in groundball outs indicates such a strategy. Within that mix of bullpen arms has been Yoshihisa Hirano.

A handful of contenders had interest in the Japanese closer this winter, but the Snakes locked him up. They’ll have him in their ‘pen for 2018 and 2019 as a result. And, quietly, he’s been extremely good out of the Arizona bullpen.

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In just about 32 innings this year, Hirano has posted an ERA of 1.42. His strikeout numbers are just a touch under nine per nine innings. You’d like to see lower walk numbers (3.41 per nine), but he’s able to compensate well. His groundball rate is just over 50%, and he’s stranding over 92% of opposing baserunners. It culminates in a stellar 0.98 WHIP. As a setup man, what more could you ask for? Not much, as his 15 holds are third among relievers. No. 1 in that regard? Archie Bradley.

So how has Hirano made the transition to Major League Baseball so smoothly? He can thank his splitter more than anything. So far in 2018, Hirano has thrown his four-seamer about 56% of the time. His splitter? About 44%. There was a slider mixed in earlier in the year, but that appears abandoned altogether. Using the splitter to play off the fastball has been an extremely effective mix for Hirano. He generates swings on the splitter over half the time, and it’s a reason he’s been able to garner so many groundballs.

There are some improvements that you’d like to see from Hirano, to be sure. The walks could come down just a touch. He is giving up quite a bit of hard contact (37.7%). But if he’s going to continue to generate such heavy groundball numbers, then there isn’t any reason for concern. The Diamondbacks found an absolute prize in Yoshi Hirano this offseason, and he’s been nothing but an asset for them in the late innings.

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It’s hard to overstate how valuable an effective bullpen can be. Especially given some of the Diamondbacks’ health and performance woes in the rotation. After all, we’ve seen in Arizona what a poor bullpen can lead to. Those woes appear in the past, however. Hirano has been an asset in using his skill set and two-pitch mix to his advantage. For now, though, he’ll likely keep flying under the radar.