Christian Yelich has some wild home-road splits

Christian Yelich is off to an unbelievably massive start. He's hitting .417/.540/1.271 with 13 homers, only one fewer than the entire Tigers offense. It's the best line in baseball by quite a bit.

Christian Yelich is off to a very disappointing start. He's hitting only .227/.306/.273 without a single homer. That's terribly below-average. It's the 147th-best line in the game. It's worse than Rio Ruiz or Grayson Greiner.

How can both of those things be true? It's because that first line is showing only his production in 14 games at home, in Milwaukee's Miller Park. The second line is what he's done in 11 games on the road. He's been two entirely different players, to a near-hilarious degree. According to the Elias Sports Bureau, he's the first player to hit his first 13 homers at home since Dante Bichette -- who hit his first 17 homers of the season at home -- did it in a pre-humidor Coors Field in 1995.

The correct answer here is that "it's not even a month into the season, this doesn't really mean anything, it's too early," and that's probably true. But when we're talking about the defending Most Valuable Player off to a historic start while doing something really weird, well, of course we're going to dig into it.

The thing is, while saying that "Yelich has 13 homers at home this year and none on the road" is true, it's also underselling it. While those 13 homers do lead the Majors, and all have come at home, we're actually more interested in his last 18 home runs, dating back to last year. Let's list them out, in reverse chronological order.

April 20, 2019 -- vs. Dodgers (Ryu)
April 20, 2019 -- vs. Dodgers (Ryu)
April 19, 2019 -- vs. Dodgers (Stripling)
April 18, 2019 -- vs. Dodgers (Jansen)
April 16, 2019 -- vs. Cardinals (Helsley)
April 15, 2019 -- vs. Cardinals (Brebbia)
April 15, 2019 -- vs. Cardinals (Mayers)
April 15, 2019 -- vs. Cardinals (Hudson)
April 7, 2019 -- vs. Cubs (Hendricks)
March 31, 2019 -- vs. Cardinals (Wacha)
March 30, 2019 -- vs. Cardinals (Hudson)
March 29, 2019 -- vs. Cardinals (Miller)
March 28, 2019 -- vs. Cardinals (Mikolas)
October 20, 2018 -- vs. Dodgers (Buehler, NLCS Game 7)
October 4, 2018 -- vs. Rockies (Senzatela, NLDS Game 1)
September 29, 2018 -- vs. Tigers (Stumpf)
September 29, 2018 -- vs. Tigers (Norris)
September 28, 2018 -- vs. Tigers (Zimmermann)

You might be tempted to notice that he's dominated St. Louis pitching, and that's true, but it's also not the point here. The point is in the fact that all of them say "vs," and not "at," which is to say every single one of those 18 home runs came at home.

On Friday, when the Brewers march into New York to kick off a series with the Mets, it will have been seven full months since Yelich's last road homer, which came against -- who else -- the Cardinals, on Sept. 25, 2018. Here's proof he did it, just so you can see him circling the bases in the road uniforms.

Since this is a ridiculous thing that's happening, let's break out some ridiculous numbers. Let's go back to Sept. 26, 2018, the first day after his St. Louis home run. Between then through Thursday's games, including the playoffs, the Majors have hit 600 road homers. George Springer has nine road homers. So does Luke Voit. Nine different Brewers have hit road homers. Six different pitchers have hit road homers. Zack Greinke has two! Yelich: None.

It's true that he may have had a homer in Anaheim earlier this month, if it hadn't been robbed by Mike Trout. But if we're going to point that out, then we have to note that he also might have had another home run in Milwaukee, if it hadn't been robbed by Cody Bellinger.

It wasn't always like this, of course. When he called the famously pitcher-friendly Marlins Park home, as he did for the first five seasons of his career, his splits were a lot closer, and he was usually slightly better on the road.

Marlins (2013-17)

Home -- .278/.363/.396 18 HR
Road -- .301/.374/.465 41 HR

Even as a Brewer in 2018, while he did hit for more power, his on-base percentage was basically unchanged.

Brewers (2018)

Home -- .324/.406/.655 22 HR
Road -- .328/.399/.545 14 HR

More importantly, as you'll see in a second, there wasn't a great deal of difference in his strikeout and walk rates, either. If anything, he whiffed a little more at home.

Home -- 10.8 percent walk rate, 21.6 percent strikeout rate
Road -- 10.1 percent walk rate, 19.9 percent strikeout rate

Brewers (2019)

It's... a little different this year.

Home -- 22.2 percent walk rate, 9.5 percent strikeout rate
Road -- 8.3 percent walk rate, 25 percent strikeout rate

Those are small samples that will sort themselves out, but there's obviously something happening here.

It's tempting to look at all this and say it's entirely about the park, that Marlins Park is death on power while Miller Park boosts it, and there's some amount of truth to that. We talked a lot last winter about how leaving Miami would help J.T. Realmuto, though that hasn't manifested itself just yet. Simply looking at traditional park factors, Miller Park is slightly above average, while Marlins Park is all the way at the bottom. But we can do a little better than that, because we have Statcast data, and we want to get to power, specifically left-handed power.

The way we'll do that is to try to get to "park value added," which is the difference between Expected Weighted On-Base Average -- i.e., what we've observed to happen across the Majors based on combinations of launch angle and exit velocity -- and actual Weighted On-Base Average, which can be read similar to OPS. We're not going to get too deep into the weeds on this, but the point here is that we can use this data to answer this question:

Which parks, in 2018-19, have seen more or less production than expected, for lefty hitters on line drives and fly balls?

Miller Park isn't the best park for this, but it's top six, and considerably better than Miami.

Those results intuitively make sense, anyway. Of course Coors Field boosts a hitter more than anywhere else. Of course the short porches in the Bronx and Houston would gain lefties a little more production than they deserve. And, at the other end, of course Marlins Park is a rough place to hit. Milwaukee has boosted lefties by +37 points on liners and flies. Miami has cost them -21 points. It's a big deal.

But it's not the only deal, is it? Yelich has repeatedly stated that he's not a proponent of launch angle, and that he's not trying to hit balls in the air.

"Honestly, there's been no change or no conscious effort to do anything different than I've done in the past," he said after a multi-homer game in Cincinnati last August.

Perhaps so. But there's evidence that something has changed, regardless, when you look at his batted ball splits, by team.

Marlins (2013-17)

Home -- 61 percent grounders, 39 percent liners/flies
Road -- 57 percent grounders, 43 percent liners/flies

Brewers (2018-19)

Home -- 48 percent grounders, 52 percent liners/flies
Road -- 52 percent grounders, 48 percent grounders/flies

See what happened there? It's true that his ground-ball rate on the road dropped by five percent, from 57 to 52. It's also true that his ground ball rate at home dropped by more than twice as much, by 13 points from 61 to 48. Yelich may not be actively trying to hit the ball in the air more, or at least he's not willing to admit it, but it's difficult to think that he's not trying to take advantage of his new home.

After all, it's so hard to hit the ball out in Miami that there was a decent argument that he shouldn't even have bothered, instead trying to aim for doubles and triples over warning-track flyouts.

"You've got to earn them," he said after hitting a Marlins Park home run in 2017. "You don't really get any cheap homers in this place."

“You’ve still got to hit them here," he said to Milwaukee media last August, comparing his two home parks. "But at Marlins Park, you really, really had to hit it.”

Perhaps so, and he's not really going to get through the entire season without hitting a road home run, or without hitting for power at all. He's too good not to, regardless which park, state, area code, or time zone he happens to be in. It has been seven months, however. Miller Park certainly seems to agree with him. At some point, a road park will as well.