J.D. Martinez Is Being Overshadowed by Mookie Betts But He Shouldn’t Be

All eyes are on a homegrown superstar in Boston, but the Red Sox have another top flight hitter to be celebrating. J.D. Martinez has been every bit as good as his 2017 season so far.

While everyone is gushing over just how good Mookie Betts is, J.D. Martinez has (somehow) very quietly put up a first month that picks up where his preposterously hot 2017 campaign ended. The former Tigers and Diamondbacks slugger has a 162 wRC+ with 6 HR, 24 RBIs, and 18 R. That pairs with a .343/.392/.593 triple slash. He’s everything the Red Sox were hoping for, but is it sustainable?

We’ll start by taking a peak at that line extrapolated over 130 games (his average per year since 2014). Now we’re looking at 28 HR, 111 RBIs, and 84 R on the season. The home run pace is obviously down, and the slugging dropped a bit because of that. But the on base percentage is up to compensate and we’re left with very similar overall production. In short, the results are spectacular.

But are they real?

Since the last time we mentioned him in an article, Martinez has dropped 1st to 4th for Brls/PA. One of the players who passed him is the scorching hot Betts. The other two are Teoscar Hernandez and Mike Zunino. Right behind Martinez is Xander Bogaerts. His average exit velocity (95.6 MPH) is tied for 3rd. Only seven hitters have more balls put into play at 95 MPH or higher. He’s still crushing the ball.

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Based on the combination of his exit velocities and launch angles, Martinez has an expected batting average of .325 and an expected slugging of .688. He had a .303 average and a .690 SLG last year. His current wOBA is .417 while his expected wOBA is a staggering .447, topping both his xwOBA from 2017 (.431) and his actual wOBA (.430). In every meaningful way, his first month in Boston is every bit as good as his 2017 season.

What will change?

Despite the similarities, there are some differences worth noting. Per Fangraphs, his pulled and opposite field percentages are both up a few percentage points while his balls hit up the middle are down. That could just be statistical noise in a sample this small. He’s also seen a massive jump in his hard hit percentage that has come entirely from his soft contact rate from last year. That will likely even out a bit as we move forward.

His launch angle is off from 2017, dropping from 15.3 degrees to 9.5. It’s very likely that number will come up and with it, his average exit velocity will likely drop by 1-2 MPH. This may also coincide with a rise in SLG as more balls hit in the air at high exit velocities means more home runs and doubles.

Finally, we’ve also seen a 3.3% drop in walk percentage to date with his strikeout percentage ticking upward a little more than 1%. Neither is likely statistically significant at this stage of the season, but the walk rate is worth keeping an eye on. As his .437 BABIP normalizes, his OBP will come down. If it’s offset by a rise in SLG, however, his wRC+ may tread water during the transition.

It’s nice when a free agent slugger actually pans out.

Despite the differences from 2017, it looks like J.D. Martinez will give the Red Sox exactly what they paid for. He’ll likely come up short of the 45 home runs he hit last year, but he’ll still hit plenty of them. And the slash stats will certainly all be there. He’s got such easy power that the aspects of Fenway Park which typically suppress home runs don’t seem to be able to contain him:

Next: Betts enters record books

That he may not be the very best hitter in the lineup will have nothing to do with any expected regression. And it appears that this will not be the first year of his eventual decline. With a month in the books and 6 HR and 24 RBI in the bank we’ll set the over/under for each at 30 and 100.

Anyone taking the under?