The Mariners Bolster Their Bullpen

It’s been a relatively quiet winter for Jerry Dipoto and the Mariners. Seemingly content to let their youngsters play (or develop in the minors), the frantic wheeling and dealing that we had become accustomed to in offseasons past has subsided this year. With their eyes set on 2021, there hasn’t been much of a need to add to their roster. But while most of their key positions are manned by players who, in an ideal world, will form the core of the competitive roster next year, the bullpen is filled with a number of question marks. The Mariners addressed that concern by signing Yoshihisa Hirano to a one-year contract yesterday.

The deal guarantees $1.6 million to the pitcher with a number of performance bonuses based on appearances and games finished. The most interesting wrinkle to his contract comes in the form of a $250,000 bonus that kicks in each time he’s traded. This “Jerry Dipoto clause” is a savvy inclusion for the veteran reliever who will likely be shopped around near the trade deadline if he’s any good at all.

After an 11-year career in Japan, Hirano made the jump to the States in 2018. In two seasons with the Diamondbacks, he was a decent option towards the back end of the bullpen. Last year, he improved his strikeout rate by almost four points but saw his FIP jump over four due to an increase in his home run rate. Through August 12, he had actually posted a 3.30 FIP with just three home runs allowed, but a nasty two-game stretch on August 14 and 16 led to a brief stint on the Injured List with elbow inflammation. He returned in mid-September, but continued to struggle, giving up four more home runs in his nine appearances after August 12.

Hirano employs a two-pitch arsenal evenly distributed between a four-seam fastball and a nasty splitter. Opposing batters swung and missed nearly 40% of the time they offered at it last year. And even when they did make contact, they simply couldn’t hit it with any authority. He allowed just five extra-base hits off his splitter and held batters to a .303 xwOBA on contact with the pitch. He had increased the usage of his splitter prior to his elbow injury but eased off using it so heavily afterwards:

Utilizing his best pitch more often certainly helped him improve his overall strikeout rate. He also added almost an inch of horizontal movement to the pitch in 2019. That extra bit of fade definitely helped the pitch’s effectiveness, especially when he was able to locate it on the outer half of the plate against lefties. In 2019, he increased his strikeout rate against left-handed batters by nearly seven points.

His fastball isn’t overpowering and it’s no coincidence that the increased usage of his heater coincided with his struggles last year. It possesses a good amount of ride even though its spin rate is rather average. He was able to add almost three points to the pitch’s whiff rate, pushing it over 20%. But that didn’t stop opposing batters from posting a .242 ISO against the pitch. Perhaps his struggles were related to where he was locating his fastball:

In 2019, the average vertical location for his fastball dropped by a third of an inch. When he’s able to locate his heater up in the zone, batters have whiffed more than a quarter of the time they swing. But less than 10% of his fastballs were located in the upper regions of the zone in 2019. Far too many of his pitches found the heart of the plate, and batters easily took advantage.

Still, despite the increased home run rate, Hirano managed to avoid allowing a ton of hard contact. His hard hit rate fell in the 94th percentile at just 29.3%. His ability to miss bats with his splitter, combined with his ability to limit hard contact, should help him provide some value to the Mariners, potentially as their early season closer. And if those skills carry over into improved results, he could bring back a useful piece in a mid-season trade. With such a low salary commitment and some potential upside, adding Hirano was a shrewd move for Seattle in an otherwise quiet offseason.