Should Red Sox fans be worried about J.D. Martinez?
The Red Sox signed J.D. Martinez to hit for power. He has yet to do so in the early goings, leaving fans wondering if he’s going to look like the guy he was in Detroit and Arizona last year. Should they be concerned?
By most measures, J.D. Martinez is off to a slow start. In eight games he has hit .226/.286/.419 with 1 HR and 4 RBI. Hardly the behemoth slugger Boston Red Sox fans envisioned when he finally signed in late February. Should he fail to start hitting, he wouldn’t be the first high profile signing to bust in Boston. Carl Crawford and Pablo Sandoval both say hello. So should Sox fans be worried about the latest big name to don the uniform?
Putting things into perspective:
While the results are far from pretty to this point in the season, there’s more we can look at than his slash line and counting stats. The most important of these is, arguably, his Statcast data. Over at xStats.org we can sort through things like exit velocity (EV) and launch angle groupings like GB%, LD%, HD%, and FB%.
As I’ve pointed out before, low drives (LD%) and hard drives (HD%) are the two most productive ranges, and fly balls (FB%) are where most home runs come from. Here’s the table I used in that article:
Hitting is a science
| Launch Angle | AVG | SLG | wOBA |
| DB% (<0) | .187 | .202 | .170 |
| GB% (0-10) | .515 | .581 | .476 |
| LD% (10-19) | .708 | .968 | .711 |
| HD% (19-26) | .554 | 1.270 | .734 |
| FB% (26-39) | .323 | .987 | .517 |
| PU% (>39) | .044 | .087 | .054 |
Last season, Martinez led MLB in the 26-39 degree range (FB%) at 23.3% among hitters with 400 PA or more. He also ranked first in the combined HD, and FB ranges at 34.3% of his balls in play. When we add all of the quality contact ranges together (everything except DB% and PU%) he falls to 21st in the league. In short, he made a lot of significant contact in 2017.
How does 2018 look?
Where does he fall so far this season? He is only at 19.1% FB and his combined FB, and HD ranges are just 28.6% with the Red Sox. That’s a significant drop. However, he has a 66.7% quality contact rate (combined 0-39 degrees) which is good for 23rd in baseball. Unfortunately, that combined rate is built on a 23.8 GB%, which is not where he wants to live.
But fear not! It’s incredibly unlikely that Martinez has forgotten how to hit fly balls or that he made a conscious decision to move away from them. The fly balls will come and that GB% will drop back down to something more normal for him. His previous three rates are 14.0, 12.9, and 15.4%.
It’s not all about launch angle!
While launch angle is a critical component in determining success on balls in play, it’s not the most important. Andrew Perpetua describes it as:
“First, exit velocity, generally speaking, means more than launch angle in terms of predicting success. In fact, you can predict batted ball outcomes using exit velocity alone. I have done so in the past, and I could predict how many runs would be scored in any given game with a good deal of accuracy. That’s another topic, though. The key takeaway is this: Exit Velocity trumps angle.”
He also points out that peak exit velocities exist between -10 and 10 degrees, which makes sense since you are most likely to square up the ball in that range. After all, most pitches come into the zone between 0 and 10 degrees.
“Well, think of it this way: you hit the ball harder if the center of the bat is lined up with the center of the ball. That is obvious enough. Well, if the ball comes in with an angle of 0-10 degrees, then your bat will need to have an angle of 0-10 degrees to achieve maximum exit velocity. So, a launch angle around 0-10 degrees is roughly the default launch angle, give or take.”
Why does this matter?
J.D. Martinez is still hitting the ball very hard. His average EV so far this season is 93.1 mph, which is slightly higher than his average from 2017 of 91.0. That was the 15th best in the majors, for what it’s worth.
Now, the slight uptick is likely due to the increase in ground balls. From the Perpetua article linked above:
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“The average exit velocity for balls hit on this [GB%] angle is 92.9 mph.”
As his FB% comes up his average EV will come down, but not by too much:
“Once you reach 26 degrees, the difference begins to show in earnest. Balls hit between 26 and 39 degrees have an average exit velocity of 89.7 mph, and those hit above 39 degrees have an average of 82.6 mph.”
The difference between balls hit in the GB range, and the FB range is roughly three mph. So he’d be right about where you’d expect based on his 2017 average.
It all adds up to…
In short, he’s still got the most crucial factor in generating good outcomes on balls in play; exit velocity. The fly balls, which are at the core of the way he revamped his swing in 2014, will come. And when they do, expect him to look a whole lot more like the slugger who led the majors in slugging percentage in 2017.
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The first nine games aren’t exactly the way the Red Sox hoped he would start the year, but he’ll come around. Probably sooner rather than later.