The Yankees need Masahiro Tanaka to correct his sinker problem

Much has been written, spoken and tweeted about the struggles of Masahiro Tanaka in 2017. After a sterling spring training, the Yankees ace has been terrible, with a 6.07 ERA and 5.46 FIP. He’s walking more batters than ever before and giving up what’s probably an unsustainably high HR/FB%.

It seems everyone has an explanation for Tanaka’s poor performance. Some say he’s injured, which I don’t think is true because it would be neglectful of the Yankees to not ensure a struggling pitcher is healthy. Some think he’s tipping pitches, even though it’s unlikely that nobody on the Yankees would notice a tip if it happened over the course of multiple starts.

Personally, I believe the key behind why Tanaka has been unlike himself is the loss of break on his pitches. As a pitcher who doesn’t have a 99 mph fastball, Tanaka has to get by with deception and a mix of multiple pitches. Brooks Baseball tracks six: a fourseam, sinker, slider, curve, cutter and splitter. However, anyone who has watched Tanaka regularly, know that the key to his approach is the sinker.

Brooks’ game-by-game PITCHf/x tracked the vertical movement on Tanaka’s sinker:

The big takeaway: four of the five games with the biggest sinker break are Tanaka’s four best starts, against the White Sox, Red Sox, Reds and Monday night against the Angels. The fifth game, a clunker against the Rays, I’m willing to write off as an outlier because no other game even comes close to that much movement. FanGraphs’ pitch values back up the Brooks’ data. If you look at Tanaka’s sinker value in 2017, the best scores for the sinker (wSF/C) come in those four games.

What makes the sinker so important? Simply put, velocity and movement. Tanaka’s sinker averages about 1.32 mph slower than his fastball, but breaks harder in on right handed batters (away from left handed batters) and doesn’t rise nearly as much as the fourseam. A batter sees a pitch and tracks the same velocity as the fourseam fastball he saw earlier in an at bat. The sinker, however, moves so differently that the ball rarely comes in at the same place, giving Tanaka an obvious advantage over the batter.

Tanaka tends to have one of the higher groundball rates in baseball, largely in part due to his ability to keep batters off balance. Over the last three years, Tanaka has been in the top 10 in the American League in groundball percentage. If he’s able to maintain the movement on his sinker, Tanaka should be able to lower his career-high 22% HR/FB rate. He’s never had a full-season rate above 16.9%, and since his groundball rate is around career average, that number should fall with an improved sinker.

The trick will be preventing home runs against the Oakland Athletics, Tanaka’s next start and a team that can hit home runs but not do much else. Interestingly enough, Tanaka’s second best game by GameScore was against the As earlier this season, which was also the game where he recorded his career-high in strikeouts.

It’s been a rough season for the Yankees ace, but with a better sinker, encouraging results from last night, and a team he’s had success against coming up on Saturday, we may see a turnaround.

Note: This 2013 Hardball Times article is a fascinating look at why sinkers move the way they do.