Keep an Eye on Jackson Merrill’s Plate Discipline

Examining plate discipline after four games isn't necessarily the best use of one's time. Baseball is a game of sample sizes and analyzing an approach requires far more than the opening series of the year. Which means that if we're talking about Jackson Merrill's plate discipline at this point, it's probably at least noteworthy. 

Within the context of his exceptional 130 wRC+ rookie campaign, Merrill demonstrated an imperfect approach. His 34.4% chase rate was 16th-highest among qualified batters. That's not good news, but at the same time, it didn't seem to matter a whole lot. While the aggression held his walk rate down to an extremely poor 4.9%, his 79.5% contact rate was well above average, as was his his 64.2% contact rate on pitches outside the zone. You can get away with that type of free-swinging when you're going to make that consistent of contact. That doesn't mean it's an ideal way to go about things, though. Contact outside the zone isn't necessarily a good thing, as players tend to hit the ball weaker when they're swinging at bad pitches. However, Merrill's .373 wOBA and .348 xwOBA on balls in play that came on pitches outside the zone were among the best in baseball. It's probably too early to say, but he might just be a very good bad-ball hitter. Nonetheless, even incremental improvement on the approach side can bump up the run production provided by Merrill's excellent activity on the basepaths.

Given that, these first four games have allowed Merrill to demonstrate a bit of maturity as it relates to the approach: 

Obviously, we're comparing 156 games and 593 plate appearances last year to...four games and 15 in the lower row. But the chase rate being down — and the whiff rate along with it — immediately presents as encouraging. Merrill's chase rate isn't just lower, it's well above the league average. Merrill has also taken more pitches in the zone, but he's still not overly patient, which is an important distinction. You don't want to strip the aggression away entirely when it led to so much success last year. The ideal version of Merrill looks reigned in just a bit.

The outcomes speak for themselves. His 6.7% walk rate, while still not great, is higher than last year's. His 6.7% strikeout rate is drastically lower. His line includes a .467 on-base percentage and 185 wRC+ (though his .462 BABIP means we should take these numbers with a grain of salt). And that's with very little power output thus far.

A somewhat-but-not-entirely-related component to the swing rates is the swing speed. Merrill's average swing speed is coming in at about the same rate as last year (71.9 mph), but his 27.8% fast swing rate is an improvement of more than six percentage points. As a result, he's experiencing quite a bit more squared-up contact. This all speaks to a guy who is entirely confident in what he's doing right now. Not that he needed the boost coming off a stellar rookie season, but when he's hacking with selective aggression with more consistent bat speed, it appears there's another level to be reached here. 

Whether it comes to fruition, of course, is going to take us quite a bit longer to discern. Again, four games does not indicate much of anything, and plate discipline statistics are notoriously sticky year-over-year. But considering Merrill's previous level of aggression, improving his selectivity at all could say a lot. There's a long way yet to go, but with a talent like Merrill, these little nuances could make all the difference.