Shota Imanaga is pitching like an ace

Among the high-end starting pitchers who signed with new clubs in the offseason, perhaps none had as much uncertainty surrounding their projections as Shota Imanaga. While Imanaga was a star in NPB for the past half-century and had a track record of success, there were many questions about how his skills would translate to MLB. This was reflected in his contract with the Cubs, which only guaranteed $23 million over two years, far from our projection of $88 million. However, over the past month or so, this 30-year-old rookie has posted the best numbers in the league.

Shota Imanaga's Stats Ranking

K% BB% ERA xERA FIP
18th 4th 1st 4th 8th
Out of 79 qualified pitchers

Through 7 starts, Imanaga has allowed only 5 earned runs. Shota Imanaga is continuing to pitch in a truly dominant fashion, proving that his pitching craft is up to Major League standards while controlling the strike zone better than anyone else. However, Imanaga is putting up different numbers than other top-tier pitchers. Let's look at Imanaga's pitch types.

A quick glance at the stats sheet reveals the high frequency with which Imanaga uses his fastball. In an era where nearly two-thirds of starting pitchers throw something other than a fastball, Imanaga's 58.4% usage rate (91st percentile) stands out. As David Adler of MLB.com pointed out, Imanaga's heater is the best pitch in the game, surpassing Corbin Burnes' notorious cutter and Tyler Glasnow's terrifying fastball. However, while the other heaters at the top of this list sit in the mid-to-high 90s, Imanaga's four-seamer averages only 92 mph.

The list of starting pitchers who throw 92 or below is quite short, and most of them are not names you would think of as strikeout masters. Adler notes that Imanaga's fastball has elite Induced Vertical Break (IVB). Triston McKenzie's four-seamer currently leads the league in fastball IVB, but it allows the highest xwOBA among such pitches (with 50+ appearances). Rather, what makes Imanaga's pitching special is its plus movement in addition to his ultra-low release point.

Pitchers like McKenzie and Ross Stripling throw from a high, over-the-top arm slot, making their backspin (and thus vertical movement) predictable for hitters. In contrast, Imanaga throws from a low, three-quarters arm angle, which results in movement that differs significantly from what would be expected from that arm angle. Earlier this week, Michael Rosen analyzed the biomechanics of Imanaga's ability to spin the ball well from an unusual release point, showing how the flexibility of his hips and lower body allows him to get 'behind' the ball and generate backspin. Across the league, no other starting pitcher has as low a release point with as high an IVB as Imanaga. Pitchers who throw from a low slot are mainly sidearmers who sacrifice carry to generate run.

Because Imanaga's four-seamer has a low release point and high carry, its vertical approach angle is the third shallowest in the league. His 12.5% swinging strike rate and 22.1% put-away rate easily exceed the league averages of 10.3% and 17.9%, respectively, and he can aim for whiffs in any count.

Although Imanaga gets many whiffs on his fastball, his swinging strike rate is far from the league-leading 20.1% of Jared Jones. For it to be the most valuable pitch in the game, Imanaga's fastball must function even when he is not fooling the hitter. At first glance, one might think that because a low-90s heater is in the zone, hitters would hit it far if they connect. In fact, Imanaga's play in NPB was often plagued by home runs, and his 2.9% home run rate (1.04 HR/9) last year was the highest in the league amid a worsening offensive environment. However, he has allowed only 3 home runs in 7 MLB starts, and according to Statcast data, this low number is more a product of skill than luck.

Fastball Contact Quality Metrics

Statistic Value Percentile
wOBA .189 98th
xwOBA .279 85th
Barrel Rate 7.6% 66th
Source: Baseball Savant

I wouldn't say the 0.65 HR/9 figure represents Imanaga's true talent (ZiPS projects him to mark 0.94 for the rest of the year), and it is certainly possible that his results will regress toward his xwOBA as the season progresses. Part of the reason lies in the shape of his fastball. A flat VAA can invite uncomfortable swings and produce weak outs. This type of fastball contributes to a high fly ball rate, but so far, opponents have not been able to charge at hits in the air. Imanaga's average exit velocity and batting average against are about league average, but his exit velocity on air-borne balls is in the 70th percentile. Also, he has the 9th lowest line drive rate among starting pitchers and rarely allows square-up contact.

Imanaga also places his fastball in spots where barrels are hard to come by. While it is true that he throws more heaters in the zone than almost anyone else, he is not just sending them down Broadway and hoping for the best; he consistently spots them at the top of the zone. His fastball thrown in the top third of the zone ranks 10th, and this area can make the flatness of the pitch play up and create the illusion that the ball is rising. Naturally, his Kirby index, which shows the consistency of his release angle, is in the 90s.

With his fastball alone, Imanaga has become one of the most effective pitchers in the league. Like his fastball, he throws this pitch with surprising precision. Many pitchers' splitter heat maps look like a giant blob, with nearly 14% of their splitters going to waste. But Imanaga repeatedly hits the optimal spots for success: at the bottom of the strike zone and just below it. His splitter location+ is 108 and his PitchingBot command grade is 57, both of which are among the best in the league.

In terms of pure shape, Imanaga's splitter is not particularly remarkable. It doesn't have the crazy horizontal movement of Kevin Gausman's, nor does it drop off the table like Jordan Hicks'. However, when combined with his high fastball, that splitter becomes truly troublesome. Because Imanaga's splitter is thrown from the same release point and angle as his heater, hitters swing thinking it's a meaty fastball before they realize it's 9 mph slower and 19 inches lower. Imanaga throws his splitter about half as often as his heater, saving it for 2-strike counts when hitters are in swing mode. Imanaga's splitter is not particularly remarkable in terms of pure shape. As a result, Imanaga's splitter has become one of the league's best whiff pitches.

The best whiff pitch in baseball

Source: Baseball Savant (minimum 50 PA)

The splitter is also essential for maintaining Imanaga's tiny walk rate, as hitters swing and miss before they can get into deep counts. Opponents have swung and missed at 47.2% of the splitters he has thrown out of the zone, which is a big reason why his overall chase rate is near the top. With a low walk rate and no wasted pitches, Imanaga's pitching also leaves great results in terms of efficiency, with the 6th fewest average pitches per inning among starting pitchers. By quickly dispatching opposing lineups, Imanaga is able to pitch an average of 6 innings per start, allowing him to go deep into games while increasing his number of appearances as part of a 5-man rotation.

Just one month into his MLB career, Imanaga has exceeded expectations and emerged as an ace. Imanaga's brilliant pitching craft has not only proven that he is at his best, but has also quieted concerns about what his downside risk might look like. When Imanaga signed, it was easy for skeptics to compare him to other pitchers with big velocity or no questions about their projections. However, there is no other pitcher who pitches like Imanaga.