From 2014 to 2016, Masahiro Tanaka ranked thirteenth in ERA among starters with at least 450 innings pitched, at 3.12. But this season has been different; he has been the seventh-worst qualified starter in the league so far by ERA, with a 5.33.
For Tanaka, this is completely unprecedented. Prior to 2017, there were just three months in his career when he pitched more than 20 innings and had an ERA over 3.50. He has had four such months already this year. Tanaka has been so bad that the Yankees are in pursuit of another top-of-the-rotation starter, even after the breakout of Luis Severino.
Tanaka's troubles start with the long-ball. He has allowed twenty-four home runs, third-most in the major leagues. He has never allowed more than twenty-five in a single season, a streak that seems sure to end. His HR/9 has almost doubled from last season to this season. And Yankee Stadium's hitter-friendly confines are not to blame. Tanaka's ERA is over a run lower at home, and he has allowed twelve home runs both at home and on the road.
Almost all of Tanaka's struggles come from an astronomically high home run per fly ball rate and an elevated batting average on balls in play.
His HR/FB rate is 22.6 percent, by far the highest of his career and the highest among qualified starters. The league average home run HR/FB rate is 13.7 percent. Since 2010, only two starting pitchers with over 150 innings pitched have had an HR/FB rate higher than 20 percent. In other words, Tanaka has been extremely unlucky when he allows a fly ball. Smart money says his HR/FB rate will come down in the second half.
Especially because, while allowing more home runs than almost anyone, Tanaka has been showing some of the best stuff of his career. His velocity on all six of his pitches are up from the 2016 season. His fastball velocity is the highest of his career, at an average of 93.2 MPH. He is throwing his sinker harder also; after dipping down below 90 MPH in September 2016, it has been just a hair below 92 MPH so far in July.
Tanaka is also getting more whiffs and allowing less contact than ever. His swinging strike percentage is 14.7, the best of his career and fourth-best in the league behind Chris Sale, Max Scherzer, and Corey Kluber. He has gotten hitters to swing at 38.1 percent of his pitches outside if the zone, better than anybody in the league.
When he does allow contact, Tanaka is allowing the twelfth-lowest line drive percentage in the league. He is still one of the most prolific ground ball pitchers in the league at 49.7 percent. He has also allowed a pop-up on a career-best 12.3 percent of his fly balls. Tanaka is avoiding line drives and getting ground balls and pop-ups at an above average rate, and still his ERA is suffering!
Although he is getting his whiffs and allowing near-optimal contact, he is allowing more hard hit balls than ever. He has allowed thirty-one “Barrels” so far this year, balls measured by Statcast as having the right combination of launch angle and exit velocity to frequently result in extra base hits, fifth-most in the league. He allowed just twenty-six in 2016. Despite already allowing more Barrels than he did in 2016, his average exit velocity is up just 0.1 MPH. This could just be a case of Tanaka allowing a few extra mistakes in the zone. Presumedly, his barrel rate will come down from the perch it’s at now, and his overall exit velocity will fall too.
Tanaka is having way too much success getting whiffs, ground balls, and pop-ups to continue having a 5.33 ERA. His xFIP of 3.73, which adjusts for a league average HR/FB rate, already suggests he has been a mid-rotation type of arm so far this season if he had a normal rate of home runs allowed. If the Yankees righty has even a tinge of better luck with balls in play, and fly balls specifically, he will recover and be the ace the Yankees are yearning for.
Dylan Svoboda is a writer for Beyond The Box Score and BP Milwaukee. You can follow him on Twitter at @svodylan.