Kevin Kiermaier, Breakout Candidate

Kevin Kiermaier has long been underrated in the mainstream baseball world. He provides value in ways that tend to get overlooked or, at least, receive less attention. You probably know, for example, that Kiermaier is an elite defensive player. You’re probably aware that Kiermaier is an above-average baserunner. You might also know that Kiermaier has recorded a league-average batting line despite having faced the most difficult pitchers and that he owns a pair of piercing green eyes.

The total package is quite valuable. Kiermaier has already produced 13.1 WAR for his career over parts of three major-league seasons. He produced more than five wins in 2015, and per 162 games, he’s a 5.8 WAR/season player for his career.

I’m guessing most in the FanGraphs community consider Kiermaier to be a star. If things go well, everyone else might believe that this year, too.

Yesterday, Baseball Prospectus editor Aaron Gleeman posted some of PECOTA’s top breakout picks for hitters in 2017. Some of them aren’t all that surprising: I think a lot of people suspect there is more in the bats of Byron Buxton and Gregory Polanco and Addison Russell. But one name on the hitters list did jump out at me, and that was Kiermaier’s.

Wrote Gleeman:

WARP has long viewed Kiermaier as one of the most underrated players in baseball and now PECOTA thinks he has a chance to add above-average offense to otherworldly defense. Last season Kiermaier upped his power and plate discipline, but it went largely unnoticed because he hit just .246 and missed two months with a broken hand. If he continues to be plus-20 runs in center field Kiermaier is a star no matter what, but PECOTA sees untapped offensive upside in the 27-year-old. At the 60th percentile he’d reach 6.0 WARP and at the 70th percentile or higher he’d be among the MLB leaders in WARP, combining amazing defense with an .800 OPS.

Kiermaier’s top age-27 PECOTA comp? Vernon Wells. While the older version of Wells wasn’t productive, the 27-year-old version recorded a 128 wRC+ as a center fielder in a six-win campaign.

If Kiermaier goes from being a plus-plus glove and league-average bat, to a player with a plus-plus glove and better-than-average bat, he will be (or should be) near the top of the AL MVP voting. He finished third in bWAR (7.3) in 2015, but 17th in AL MVP voting.

So is this breakout possible? Maybe it’s already happening.

Last season, Kiermaier more than doubled his walk rate, which jumped to 9.7% from 4.5% in 2015. The improvement was the the product of an improvement in Kiermaier’s out-of-zone swing percentage by five points, which he lowered from 32.8% to 27.9%. His strikeout rate remained steady, as did his swinging-strike percentage.

And while his plate discipline improved, he also began to lift more balls into the air, which is generally a good thing for hitters. After posting GB/FB ratios of 1.71 and 1.63 his first two years in the majors, Kiermaier produced a 1.11 GB/FB ratio. (That said, he was also the anti-Votto, with a 25% infield fly-ball rate, which was highest percentage in the game among hitters with at least 300 plate appearances.)

His pull percentage also jumped — to a career-best 49.5%, an eight-point jump from his 2015 mark (41.3%).

Consider this video evidence of a home run against an up-and-in fastball location:

Kiermaier saw more changeups than he did in 2015, and was more effective against them, batting .250 and slugging .438 versus changeups in 2016, compared to a .218 average and .346 slugging mark in 2015. Some visual evidence of Kiermaier doing damage to a changeup:

Moreover, his 15-game rolling wOBA has the look of a player slowly improving over the course of the last two seasons:

Kiermaier is probably never going to be an elite offensive force. His average exit velocity last season of 89.7 mph was near the league average (89.5 mph), after an 87.8 mph average in 2015. He had a pedestrian rate of barrels per batted balls (4.2%) last season. Statcast suggests there is a cap on his offensive upside.

But perhaps we saw some signs of Kiermaier acquiring new offensive skills and better learning to hit in the majors. Perhaps PECOTA is right and there is more in his bat, offensively. ZiPS sees Keirmaier as largely the same player for 2017, posting a 101 wRC+. But if PECTOA is right, Kiermaier won’t be underrated any longer, anywhere.