Miami Marlins left fielder Christian Yelich quietly had a terrific 2014 season. Just 22 years old, the 23rd pick in the 2010 draft hit .284/.362/.402, scored 94 runs and won a Gold Glove in his first full season in the majors -- not bad for a former high school first baseman. (I'd like to know who played outfield on that team.) The defensive metrics backed up the Gold Glove, helping Yelich to 3.6 Baseball-Reference WAR and 4.3 FanGraphs WAR.
Yelich started 138 times in the leadoff spot, but the Marlins acquired Dee Gordon in the offseason, so Yelich likely moves down to second or third in the order, where the expectation may be that as he gets older he'll add some power after hitting just nine home runs in 2014.
In Yelich's case, however, it's not just about adding strength or learning to turn on the ball. He has a natural inside-out swing, as you can see from the hit chart to the right: 59 percent of the fly balls he hit went to left field and just 8 percent to right field. But the kicker is he doesn't hit that many fly balls to begin with. Among players with at least 350 plate appearances, Yelich had the fourth highest rate of ground balls to fly balls in the majors:
1. Everth Cabrera, 5.45
2. Ben Revere, 4.51
3. Norichika Aoki, 3.63
4. Christian Yelich, 3.42
5. Dee Gordon, 3.13
6. Derek Jeter, 3.06
7. Adam Eaton, 2.96
8. Ichiro Suzuki, 2.95
9. Howie Kendrick, 2.85
10. Elvis Andrus, 2.81
That's not a list of power hitters. The group combined to hit 32 home runs, half of those from Yelich and Kendrick. While most of these guys are slap-and-dash speedster types, Yelich is 6-foot-3, 200 pounds. He at least has the frame to hit for more power if he can hit more fly balls.
Let's do a little study. FanGraphs has batted-ball data back to 2002. I did a search for all players 23 or younger, at least 350 plate appearances. Is there anybody who had a ground ball-to-fly ball ratio similar to Yelich's who developed power?
Part of the problem with finding a comparable player is Yelich's ratio is actually second highest on the list, behind Revere's 2011 season. So he's already a pretty extreme outlier. The top of the list includes a bunch of Andrus seasons and a couple of Jose Tabata seasons. Tabata hit .299 as a rookie at age 21 but his power never developed. Increasing the age cutoff to 25 doesn't offer much help (or hope).
There are a couple of players lower on the list, however, that provide hope that Yelich could develop double-digit home run power:
In 2004, 23-year-old Alex Rios hit .286 with one home run in 426 at-bats and a ground ball-to-fly ball ratio of 2.49. He's even built similarly to Yelich, tall and lean. He developed into a consistent 15- to 20-homer guy, three times topping 20.
In 2003, Carl Crawford, in his age-21 season, had a ground ball-to-fly ball ratio of 2.23 while hitting five home runs. He's reached double digits in home runs seven times -- peaking at 19 -- plus a ton of triples. But note that he didn't hit as many grounders as Yelich.
As far as older players goes, Jeter is an interesting comparison. Since 2002, he had a 3.00 GB/FB ratio in five seasons, but he maxed out at 15 homers in those years. When he hit 23 home runs in 2004, his GB/FB ratio was 1.47.
Obviously, there are examples of players who added power as they matured. As one example take Kirby Puckett, who hit four home runs his first two seasons in the big leagues and then hit as many as 31 in a season. We don't have his exact batted-ball data in those early years, but Baseball-Reference.com does track groundouts and fly outs. Here's Puckett his first four years:
1984 (0 home runs): 1.55
1985 (4 home runs): 2.17
1986 (31 home runs): 1.10
1987 (28 home runs): 1.50
Yelich's ratio in 2014 was 2.43.
Does that mean he'll never develop power? I'm not going to say it won't happen. A positive sign is that in his 62-game rookie season in 2013 his ground ball-to-fly ball ratio was 4.58, so he did improve in 2014. He'll have to drop that total a lot more and also learn to the pull the ball when he does hit it in the air, otherwise he's just Eric Hosmer.
Aside from that, the big positive is he's already a good player as he enters his age-23 season, with a sound approach at the plate and excellent defense. Even if he doesn't turn into a 20- to 25-homer player, he's going to create a lot of runs with high batting averages and excellent on-base percentages.