J.D. Martinez Switches Coasts

Last Saturday, the Dodgers reportedly agreed to a one-year, $10 million contract with J.D. Martinez, to presumably act as their every day DH. The 35-year-old is coming off a disappointing season, posting his lowest wOBA over a full season since his debut years in Houston, before he transformed into an elite hitter. Will the move to Dodger Stadium fuel a rebound? Let’s check the park factors to find out if his new home park might boost his performance.

Surprised? I am, somewhat. It’s nearly a clean sweep for Fenway, which doesn’t bode well for this park switch helping Martinez’s chances of rebounding. However, I think the shape of the performance change the park switch might drive is important. Let’s dive into the individual factors.

It’s a clean sweep for Fenway on the non-home run hit factors, which is no real surprise. The Green Monster turns lots of would-be fly outs into singles and doubles, so it’s a BABIP haven for hitters. However, Martinez hasn’t actually followed those factors. Throughout his Red Sox career, Martinez has posted a .338 BABIP at home, but a .347 mark in away parks! That was not what I was expecting. Diving into his fly ball splits, we may have learned the reason — Martinez actually goes the opposite way with his fly balls more frequently than the league, and pulls his flies less frequently. So he’s not benefiting from the Green Monster, because he just doesn’t hit his flies that way as often as other hitters, and his splits are similar both home and away. So perhaps he won’t lose as much BABIP as you might expect by looking solely at the park factors.

Moving along to the home run factors, we stumble upon the only Dodger Stadium win. Did you know it was such a strong home run park for right-handed home runs?! While Fenway’s Green Monster giveth in terms of BABIP, it also taketh away, as fly balls have to travel high enough to clear the wall to be a home run, while lots of balls get knocked down by the wall that would have gone over the fence, if the fence was of normal height. But once again, Martinez isn’t following the factors as he has posted a slightly higher HR/FB rate at home than away. That said, clearly moving to a park that inflates right-handed home runs is a good thing. While I’m hesitant to recommend reducing his BABIP projection from the move, I think his HR/FB rate forecast should be increased.

The strikeout and walk factors are next and the strikeout factors are nearly identical. Dodger was neutral, while Fenway slightly reduced them. Martinez’s strikeout rate was almost identical home and away during his Red Sox years. I wouldn’t make a change to his strikeout rate projection due to the park switch. Interestingly, Martinez has walked meaningfully more often in away parks than at home, despite Fenway sporting a neutral walk park factor. Dodger actually suppresses walks, which isn’t great for someone whose walk rate has slipped since peaking in 2019. I would slightly reduce his walk rate projection.

Next up are the batted ball type factors. We find that Dodger both suppresses line drives and inflates pop-ups. That’s not good. This is especially negative when compared to Fenway that increased line drives and slightly reduces pop-ups. During his Red Sox career, Martinez has actually been far better at hitting line drives at home vs away, but has near identical IFFB% splits. It’s possible the much higher LD% at home was an approach change so he could hit liners off the wall for an easy single or double. That higher LD% at home makes it even more baffling that he’s posted a lower BABIP at Fenway.

Finally we arrive at our summary factor, Basic, which is the five year run scoring factor. Here, we find Dodger slightly suppresses offense, thanks to its hit suppression abilities, while Fenway meaningfully inflates run scoring, thanks to its hit inflation abilities. I didn’t expect the park to diverge that much, as I figured the better home run environment in Dodger would at least partially offset the reduction in hits, and make the Basic factors much closer.

Overall, I’m unsure whether Martinez’s BABIP forecast should get nicked or not. For nearly any other hitter, it would be an obvious call, but Martinez hasn’t seemed to benefit from Fenway’s BABIP-inflating ways. Then again, Dodger does clearly suppress hits, so even if he didn’t benefit from Fenway, Dodger could still hurt him. What’s a little more clear is that the move should help his HR/FB rate rebound after he posted his lowest mark since a partial 2013 season with the Astros, before he became the current version of himself. Since he also goes to another strong lineup, I think this is another case of his overall fantasy value remaining relatively stable, while the shape of his performance (batting avg down, home runs up) changes.