How rare lefty splitter has helped fuel Shota Imanaga's historic start for Cubs

CHICAGO — Five years ago in Japan, Shota Imanaga searched for a new pitch.

He wanted to incorporate something that would use the same arm path as his four-seam fastball. Imanaga didn’t like his tendency to pull his arm down when throwing change-ups, so he tinkered. The left-hander landed on a split-finger grip that felt good in bullpen sessions, and eventually he threw it in games.

Once he saw Nippon Professional Baseball hitters’ reaction to the splitter, Imanaga knew he had a potentially great pitch.

Since he joined the Chicago Cubs rotation this year, Imanaga’s splitter has been nearly unhittable with a 47.7% whiff rate and a .177 expected average. San Diego Padres hitters whiffed on 15 of the 24 splitters they swung at from Imanaga in the Cubs’ 3-2 walk-off win Tuesday night. Jurickson Profar’s two-run homer in the eighth inning — well-located down and out of the zone — was only the second extra-base hit Imanaga has allowed on the pitch this season.

The splitter has played a key role in the must-watch beginning to Imanaga’s major league career. His 1.08 ERA leads all starters, and only two pitchers since 1913, when earned runs became an official statistic in both leagues, had a lower ERA through seven career starts: the Boston Red Sox’s Dave Ferriss in 1945 (0.57) and the White Sox’s Cisco Carlos in 1967 (0.89).

The nastiness of Imanaga’s splitter goes beyond his elite command. Big league hitters aren’t used to seeing lefties throw the pitch.

Only 16 lefty starters have thrown a splitter since the start of the 2008 season. Five of them — Jorge De La Rosa, Manny Parra, Aríel Miranda, Randy Johnson and Erik Bedard — threw more splitters than Imanaga has, according to Baseball Savant. But no lefty in that span came close to using it as frequently as Imanaga relies on his splitter, which accounts for 30.3% of his pitches thrown.

Even when expanding to include lefty relievers, Imanaga already has thrown the 13th-most splitters over the last 17 seasons and ranks second in percentage of splitters thrown.

“For me the splitter being effective and dangerous, it’s a fine line because if I miss, then the hitters are a lot stronger here so they’re going to hit it further,” Imanaga told the Tribune through interpreter Edwin Stanberry. “But the most important thing for me, since I do throw my fastball up in the zone, having that in the hitters’ head is effective because then I can go up and then down low.”

Although he uses a splitter grip, Imanaga thinks of the pitch as a change-up. When on the mound, he doesn’t feel like he’s throwing splitters, a mentality that seemingly helps him throw it for strikes.

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