Christian Yelich took a significant step forward as a hitter last season: His home run total jumped to 21, entering double digits for the first time and effectively doubling his career total (20 HR coming into the season). It wasn’t just an increase in home runs either, Yeli’s ISO (slugging % minus average) jumped 60 percentage points up to .185, a massive increase over one season.
Usually when a player’s power spikes like that there are a few explanations that lead to drawbacks in other ways. They might be swinging earlier in the count, leading to a higher K rate and lower walk rate. Changing to a more pull-heavy approach, which drives batting average on balls in play (BABIP) down as the batter becomes the victim of the shift more frequently. Or, selling out contact for power, leading to a higher whiff rate, and often a lower BABIP. In this case, none of these things is true.
Yelich’s non-power related batting stats remained essentially the same. His walk rate actually went up, while his K rate and his BABIP remained effectively equal to his 2015 mark.
The change was all gains no drawback. As a result, Yelich saw his wRC+ go from good at 118 to very good at 130. A somewhat amusing side note, Yelich had exactly an 118 wRC+ in 2013, ’14, and ’15. That’s crazy.
The 2.0 fWAR jump from 2.4 in 2015 to 4.4 in 2016 was also nice to see. It’s still not as high as his career best in 2014 but that was due to sliding defensive production: His hitting was better across the board.
So where did the improvement come from? Well, there are several explanations.
One aspect is a subtle but important adjustment in his swing. In previous years, as Yelich brought his bat through the strike zone he pushed with his top hand, attempting to generate force with his arms. It hadn't yet led to any problems or downturn in production but it was something that could be a harbinger of a drop off should other aspects of Yelich's skill set or physical ability deteriorate. In the present, it did put a cap on his power potential and most likely affected his batted ball profile. In 2016, Yelich was able to make a slight adjustment in regards to how he used his top hand to turn and release the bat, allowing the power he generates before launch to be utilized more effectively. There is more to be unlocked mechanically but this was an important first step and it is always encouraging to see players who are already successful major league hitters make an adjustment that takes them to another level.
Though the change was subtle, the results were massive. Yeli’s ground ball rate fell to 56.6%, the first time it’s been below 60% in his career, and his fly ball rate increased to 20%, compared to just 15% in 2015. He’s always hit the ball hard, it was just a matter of getting the ball in the air where it can do more damage. Among hitters that produced at least 50 flyballs last season, Yelich ranked 3rd in exit velocity with a 96.6 MPH, behind only Josh Donaldson and Nelson Cruz.
The other part that of Yelich’s improvement came from his ability to match his swing rate to the number of pitches he saw in the zone. Consider this graph:
The point there isn’t that the graphs overlap, that would be madness, but notice how closely the hills and valleys match. Here’s the same chart from 2015 for context.
It’s a significant change. Beyond just being an improvement over his previous record, Yelich’s ability to adjust was among the most impressive in recent memory. When you’re swinging at strikes and taking balls you’re bound to find yourself in a position to do damage, and that’s exactly what Yelich was able to do last season.