Masahiro Tanaka is still searching for his splitter

After a pair of stellar starts to open the 2019 season, Masahiro Tanaka has returned to his career tendencies, pitching efficiently, save for a home run hiccup to provide a noticeable blip on the radar. Tanaka has surrendered at least one home run in each of his past five outings, and while the right-hander has still been effective overall, he hasn’t shown the level of dominance he expressed over his first two starts of the year.

A culprit behind Tanaka’s mild regression is the lack of bite in his trademark splitter. Tanaka’s split finger fastball (47.7 total runs above average) has been his most valuable pitch during his career aside from his slider (58.0), per Fangraphs, which uses pitch value as a way to determine how many runs a pitcher has allowed or prevented using a specific pitch. This season, Tanaka’s splitter is his least valued pitch (-5.2), with the next lowest coming in at -1.0 (curveball). What’s behind this sudden change in efficiency for a pitch that terrorized hitters since he broke onto the scene in 2014?

First, when it comes to a splitter, many will assume a lack of efficiency means the pitch has lost its “bite.” Has Tanaka’s splitter lost its split? Taking a look at its average vertical break and spin rate this year, the answer is no. Tanaka’s splitter has seen an increase in spin rate (from 1,468 to 1,532 RPM) and vertical movement, while maintaining the exact same velocity as it did last season.

A possible explanation for the drop in efficiency emerges when one looks at the location of Tanaka’s splitter. Take a look at the first picture, which shows the splitter’s heat map this season, compared to the second, which shows where Tanaka located the pitch from 2014 to 2018:

It seems as though Tanaka’s splitter has started to leak into the lower quadrant of the strike zone, and in the height of the launch angle era, where hitters look to drive pitches at the knees for home runs, Tanaka has found himself in trouble at times. Remember when he pitched against the Angels last week, and threw this meatball of a split finger to Kole Calhoun?

The results, of course, have not been good. When you’re locating a put-away pitch in the sweet spot of the strike zone, it’s going to get mashed. Now consider the swing-and-miss rate on Tanaka’s splitter this year, followed by the xSLG against the pitch:

These obviously don’t look like promising trends, but on the bright side, location is an easier fix than rediscovering movement or velocity. Both of those still seem to be there for Tanaka, and it’s just a matter of keeping the pitch down and in the dirt. Tanaka has been using his slider more often as his splitter has lost efficiency, but a return to form on his signature pitch will help him look like the pitcher he was over his first two starts.

Tanaka’s pitch value on his splitter has dropped consistently since his second start of the season, but the blueprint for the pitch is still there. Should he return to form and bury that splitter below the knees and in the dirt, it will be a great way to complement his slider. We know it’s possible, because we’ve seen it this season.