MILWAUKEE -- Monday's Brewers home opener happens to fall on the anniversary of Travis Shaw's first batting practice at Miller Park. He returned to the clubhouse that day with wide eyes. After two years of home games at Boston's Fenway Park, where Pesky's Pole is tantalizingly close but the rest of right field is spacious, Shaw had a feeling that hitting at home was about to get fun.
Now comes Christian Yelich, fresh off a five-hit performance in Saturday's sweep-clinching win in San Diego. Let's just say that Shaw has a good feeling again.
"I think he can hit 30 homers, personally," Shaw said. "He's got some juice."
That's what happened for Shaw last year, and for Eric Thames. Both were left-handed hitters brought in to help balance a right-leaning Brewers lineup, who tied for the team lead with 31 home runs apiece. Shaw nearly doubled his power production from a year earlier in Boston, when he hit 16 home runs in 64 fewer plate appearances.
Yelich is trading 81 home games in one of baseball's toughest run-scoring environments for one of its best, as MLB.com's Mike Petriello explored in depth soon after the trade with Statcast™'s expected wOBA metric. The simplest explanation does not require advanced statistics, but merely a tape measure. At Miller Park, the fence is about 18 feet closer to home plate in the right-field power alley -- 374 feet in Milwaukee vs. 392 feet in Miami.

Yelich hits to all fields, so when MLB.com dropped his 2017 batted balls of at least 300 feet onto a diagram of Miller Park, it did not produce a significant number of would-be home runs. But pitcher-friendly Marlins Park did seem to impact Yelich's offense; in his first five-plus seasons in the Majors, all with the Marlins, he hit more than twice as many home runs on the road (41) as he hit at home (18) with a relatively even number of opportunities (137 more at-bats on the road). In 2017, he slugged .401 at home and .472 on the road.
The question is whether Yelich will change to suit his new environment.
"I don't know if his swing was tailored to Marlins Park and that's why he hit so many ground balls," Shaw said, "but I think his true power potential is going to come out this year."
Yes, the ground balls. Yelich is an outlier in an era in which hitters spend entire offseasons analyzing data and adjusting their swings to lift the baseball in the air. Among baseball's batting-title qualifiers last season, Yelich's 55.4 percent ground-ball rate was sixth-highest. Of the 100 players last season with at least 400 batted balls, Yelich had the third-lowest percentage of "air balls" -- those hit with a lunch angle between 10 and 40 degrees, which most often produce home runs.
It works for Yelich because he hits the ball so hard (see Saturday's five-hit game). Among left-handed hitters with more than 250 batted balls last season, Yelich ranked fourth in average exit velocity (90.4 mph) and second with a 45.9 percent hard-hit rate. Among all batters, Yelich made more hard contact than all but four players in the Majors, and more than former Marlins teammates Giancarlo Stanton and Marcell Ozuna.
Slowly, his proclivity for ground balls may be changing, perhaps naturally as Yelich gets bigger and stronger. His average launch angle has ticked up in each of the three years that Statcast™ has been in service -- 0.0 degrees in 2015, 2.5 degrees in '16 and 4.7 degrees in '17 -- but still is well below the 11.1 degree Major League average. At the same time, his ground-ball percentage has ticked down.
Shaw quickly saw the benefit of pulling the ball in the air at Miller Park. Will Yelich have the same realization?
"He said, 'You'll see,'" Yelich said. "I've played there a bunch, and it's not a bad hitter's park, that's for sure. I actually don't think I've played well there, but I think that's more a credit to how [the Brewers] have pitched me.
"I'm excited. It will be a change going to a hitter's park after being at a pretty good pitchers' park in Miami. I guess we'll see as it gets underway. It might be easier to stay within your approach when you're rewarded for it every once in a while."
Which brings us to the more hypothetical reasons to believe Yelich's power will surge this season. In theory, he is coming into the prime of his career in his age-26 season and is already, as manager Craig Counsell put it during Spring Training, "a complete baseball player." Counsell has another theory relevant to Yelich: Long-legged players take longer to reach peak power. Think Jayson Werth, Counsell said.

Yelich already is showing signs of adding power. He hit a career-high 21 home runs in 2016 and hit 18 in 2017.
"I've always had the opinion that for taller hitters, it can take little while longer to sync that part of your game up," Counsell said. "It's just longer levers. It's more difficult with longer levers. It's the same with taller pitchers."
All of these factors went into the Brewers' decision to part with four premium prospects, including another lanky outfielder, top prospect Lewis Brinson, to land Yelich in a Jan. 25 trade with the Marlins. The Brewers control Yelich for the next five seasons, which club officials hope prove the best years of his baseball life.
"When we think about when baseball players come into their prime," Counsell said, "that's what gets people excited."