Going Deep: Derek Dietrich Is Having a Month

(Photo by Rich von Biberstein/Icon Sportswire)

The Miami Marlins‘ Derek Dietrich has been on a tear the last 30 days. During this stretch, he is leading all qualified MLB hitters in batting average, besting the likes of Mike Trout and Paul Goldschmidt who themselves are having a great month in their own right. Allow the following clip to be our segway into the bedlam of contact Dietrich has been displaying. Can you presuppose what I’ll be leading with?

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If you guessed incredibly bad fielding, you’d have a point but also be wrong. Though Dietrich isn’t a fielder you’d write home about, we aren’t concerning ourselves with his defensive (ahem) ineptitudes; unless the basis of your argument, once you finish reading this, is going to point at the 1.2 WAR Dietrich is sporting and poo-poo my research.

We are going to look into how Dietrich has been, somewhat noiselessly, one of the hottest hitters in baseball as we prepare put the month of June in the books.

So the topic I’ve needlessly (annoyingly?) kept at bay is BABIP. Dietrich has boasted a BABIP of .500, which is not at all in line with his .311 career average and indicative of eventual regression. His expected metrics show a fair separation between BA (.402) and expected batting average (.329); nothing drastic as his BABIP would lead you to believe. What’s more interesting is when we view his average exit velocity (89.9MPH) and launch angle (19.6^o) on Chart 1; we see an xBA of .212 with just 14% of hits under the aforementioned metrics ending up as extra-base hits.

Then we look at Dietrich’s spray chart for the last thirty days. Chart 2 shows most of his hits landing safely in the outfield where Chart 1 shows typical outs. A high BABIP but low BA-xBA difference means there is a conflict of interest when it comes to luck and skill (see Carson Cistulli’s latest Fangraphs post). Regardless of what school of thought you support, he’s completely locked in right now.

For the contact displayed on Chart 2, he’s been hammering line drives just over 38% of his at-bats and doing so while hitting an astounding .815, good for third overall with hitters that have at least 20 PA with line drive contact. It’s not a massive change for Dietrich but his LD% is up this year; at least 5% higher than his three-year average of 21.4%.

Have a look at Chart 3, his contact type, with special regard paid from game 40 and on where we see a sudden change.

Dietrich’s hard-hit rate has also improved this season, currently up to 38.3%. That increase is helped by his 42.7% rate during this 30-day stretch. Chart 4 shows his ISO has been rising, but inconsistently so, and since May 20th (the hastily-drawn black ‘x’ marks his career average).

What we know from this point is that Dietrich has been successfully making excellent contact with plenty of pop behind it; not just the last couple of weeks, but for most of the first half of 2018. That pop is centered around line drives, which have allowed him to bear the fruits of an unsustainable BABIP. Is there a correlation? Let’s find out.

I’ve taken all qualified hitters from 2013 to the present day and looked at their BABIP compared to line drive rate. The following data for both Chart 5 and 6 are made up of 360 samples.

With this relationship, we have an R² of .20. Not great but certainly enough to assume they can be loosely associated.

Then what about batting average and LD%?

This time we see R² produce a much weaker correlation; 0.119 to be exact. Hitting more line drives can, but usually don’t, result in a higher batting average but, at the very least, improve it slightly.

So Dietrich is just in a zone; a very productive and sustained one at that. You can’t expect him to stay there for much longer, especially if the gap between his BA and xBA grows quickly. Right now, lucky or not, the ball is traveling and falling perfectly for Dietrich.

I’ll leave you with this; Dietrich’s directional hitting. You can’t quite call him a ‘pull hitter’, though he’s come close to the 50% pull rate in the past. Right now, he’s demonstrating the concept of an ideal spray hitter. Looking at Chart 7, see how everything starts to come together around early/mid-June? He was hardly going opposite field at all earlier in the season, now he’s doing it with more regularity and beating the defense to boot.

If the Marlins are preparing to use Deitrich as trade bait, and they should, he’s doing a spectacular job setting the stage for himself and the organization.