Hisashi Iwakuma has been a very good pitcher with the Mariners, with one fatal flaw, the long ball. Despite pitching most of his games in a pitcher friendly ball park, he has given up 17 homers in both years in the Majors so far. So looking at data from both 2012 and 2013, I wanted to look at his home runs and see why Iwakuma is so home run prone and whether or not he can fix it.
Here are the locations of the pitches he has given up homers on, labelled with the MLBAM tags:
There are a lot of arm side fastballs here, both high and low, along with some hanging sliders and sinkers. There are a few splitters, but perhaps even more alarming than all the fastballs hit out of the park are the sliders hit out of the park, especially the well located sliders (perhaps you could argue that they aren’t glove side enough, but there are several low ones).
But how do his home run locations compare to his other average locations. Here Iwakuma’s average locations, based on result, labelled with average velocity
Not surprisingly, even though he keeps the ball low on average, it is the highest pitches that are being hit for home runs. His average contact is a little higher than all his pitches on average, and also more arm side (even though the home runs are a little more glove side). The contact plays are a little harder in velocity than the average pitch, so the higher and harder pitches (read fastballs and sinkers) are the ones that are hit. His whiffs come on glove side pitches that are a little slower (there really isn’t much deviation in velocity) and lower (read the splitter).
More of the homers have come against right-handed batters (4.4 % to 2.6 % against lefties), probably because of the splitter neutralizing lefties (his OPS against both is about equal). We see this come out in the spray chart of batted balls Iwakuma has given up (via Katron.org, just 2013 at Safeco)
Despite facing more left-handers than righthanders, Iwakuma is giving up a lot of balls to left field, suggesting righties pulling the ball. So I thought it might be helpful to see how he is pitching right-handed batters:
So Iwakuma is able to keep the ball glove side, away from right-handed batters on average. He doesn’t throw a lot of curveballs, but he isn’t getting them down. When he gives up homers, not surprisingly, especially considering the spray chart, he is keeping the ball arm side and high in the zone. The sinker is getting somewhat down, and the fastball is getting glove side, but when he is getting in trouble, it is with these pitches against right-handers.
In a previous article this year, I noted that Hisashi Iwakuma was throwing pitches basically right down the middle without great velocity and getting away with it. Now, it doesn’t appear he is. He still has a solid strikeout rate, and he isn’t walking very many batters, but he has a home run problem that I think is directly related to his fastball velocity. Unless he is willing to throw more pitches out of the zone (he is 14th in zone % out of 93 qualified pitchers) and walk more batters, this is just going to be a problem for Iwakuma. Of course, this would have undesired side effects as well. Despite the good splitter, his stuff isn’t overpowering on the whole, and he is just going to be hittable at times (the low BABIP aside). If he keeps the walk rate low and keeps missing some bats, then you can live with the home runs, as there won’t be many runners on base when the home runs are hit.