Kevin Kiermaier is underrated. How do I know? I guess I don’t know, but by and large, Kiermaier is not considered one of the best players in baseball. This despite having performed like one of the best players in baseball. The last three years, by WAR, Kiermaier has been as valuable as Robinson Cano, Andrew McCutchen, and Yoenis Cespedes, all while collecting far fewer plate appearances. Kiermaier is projected to be as valuable as Carlos Correa and Giancarlo Stanton. The numbers are in love, and they paint a certain picture. Kiermaier is presently the most important player on his team.
Being a FanGraphs reader, you at least kind of know what Kiermaier is about. He’s underrated because his standout skill is outfield defense, and he swings a roughly average bat. I’ll say this: Although Kiermaier’s UZRs are extreme, DRS loves him even more. He has a career outfield UZR of +60. He has a career outfield DRS of +81. That would be another two wins, more or less.
So, the major reason Kiermaier’s underrated: His strongest skill is underrated. Beyond that, it doesn’t help him that he’s played for a nationally invisible ballclub. Let me add a third reason. For this part, I’m going to call in Jorge Soler.
Between Kiermaier and Soler, who was the better hitter last season? Let’s take this all the way back to the first days of your baseball education. Kiermaier batted .246, and Soler batted .238. Edge Kiermaier, right?
No, that’s stupid. Not all hits are created alike, and you can’t just forget about walks. Kiermaier had a .741 OPS, while Soler came in at .769. Advantage Soler!
There’s still room for improvement. OPS doesn’t properly weight the significance of getting on base. Kiermaier notched a wOBA of .323. Soler, meanwhile, came in with a wOBA of .333. Soler’s advantage remains intact.
Just one more step, yes? Gotta account for environment. Soler hit more, but he also played in places that yielded more productive hitting in general. Tampa Bay is not a good hitter’s ballpark. So we’re left to consider Kiermaier’s 104 wRC+, against Soler’s 106. Soler retains a slight advantage. Really, though, the difference is negligible, and the players were tied.
That’s about as far as we tend to take things. We’ve walked through all the usual adjustments. But there’s one more adjustment that’s almost never made. It’s almost never made because data is practically impossible to track down, but hitters in the majors don’t face equivalent pitchers. There can be strength-of-schedule issues, which, yeah, of course there would be. Most of the time, it isn’t that important, and the landscape is even enough. Yet there are always players at either extreme, and you can look at them at Baseball Prospectus.
That linked report shows you the average pitcher a hitter faced in a given year. You see average BA, OBP, and SLG allowed, along with True Average (sort of their version of wOBA) and RPA+ (sort of their version of wRC+). The higher the average RPA+ allowed, the worse the average pitcher. So, I linked you to the 2016 report. There were more than 300 players who batted at least 250 times. According to this information, at least, Kiermaier was tied with teammate Logan Forsythe for having faced the toughest slate of pitchers. Why wouldn’t we think that would matter?
You can go past just this last season, too. Kiermaier in 2015 ranked at 288 out of 295, in descending order of RPA+. And in 2014, Kiermaier ranked at 271 out of 302. Provided that this information is accurate and reliable, Kiermaier has faced a bunch of tougher-than-average opponents. So the version of him we’ve seen has hit less than you’d expect of another version treated more, I don’t know, fairly.
Let’s switch back to 2016. Look at that leaderboard again. Kiermaier is at the bottom, because he apparently faced the best average pitcher. And Soler is at the top, because he apparently faced the worst average pitcher. Soler’s data point is particularly outrageous. This post could probably be about him. His average opponent was good for a 116 RPA+, and no hitter has faced such an easy slate of opponents since at least 1969, given a minimum of 250 plate appearances. The fact of the matter is that, while Soler hit well enough, he was already set up to succeed.
Let’s pull in a more familiar measure. A FanGraphs measure — specifically, ERA-. That’s park-adjusted ERA, on a scale normalized to 100, where better pitchers are under 100 and worse pitchers are over 100. Two years ago, Soler’s average opponent had a 97 ERA-. Last year, his average opponent had a 112 ERA-. That presumably helps to explain how Soler made gains in walks, strikeouts, and power. And Kiermaier? This past year, Kiermaier’s average opponent had a 96 ERA-. It’s not like he was facing ace after ace after ace, but little things add up over a full season. For 2016, Kiermaier’s average opponent was Sean Manaea, or Jeff Samardzija. Soler’s average opponent was Doug Fister, or Jorge de la Rosa.
Which gives you one more thing to think about beyond the slight difference in wRC+. Though Soler was better there by two points, he was facing worse pitchers, and therefore presumably worse pitches. Worse pitches are easier pitches to hit, or to take. Adjusting for opponent moves Kiermaier out in front. He’s even better than he seems, and he just needs a different schedule to show it.
It’s not the difference between Kevin Kiermaier hitting like Kevin Kiermaier and Kevin Kiermaier hitting like Mike Trout. His stat line still mostly reflects who he is, and even with a basically average bat, Kiermaier is a saber-stat superstar. But among the things true about him is the fact that, since Kiermaier emerged in the majors, he’s faced a lot of better-than-average pitchers. That would’ve pushed his offense down, in effect pushing his estimated value down. Kiermaier, incredibly, is even better than his WAR. And Jorge Soler? At least he’s got tools.
Jeff made Lookout Landing a thing, but he does not still write there about the Mariners. He does write here, sometimes about the Mariners, but usually not.