The Major League leader in home runs plays his home games a mile high, in Coors Field. Actually, the two leaders in home runs both play for the Rockies, and that's a story that often writes itself -- offensive stats at altitude tend not to be trusted, and offensive stars there tend to be overlooked.
Maybe that's true for rookie sensation Trevor Story, since we haven't seen enough of him to say what he'll really be and nine of his 10 home runs have come in either Arizona or Colorado. But for Nolan Arenado, who leads the Majors with 11 homers in 2016 and is second only to Chris Davis with 47 over the past calendar year, it's not quite as simple as that -- and for all the focus on how the unquestionably great Manny Machado has ascended into the Mike Trout /Bryce Harper echelon of young talent, let's not forget about what Arenado is doing with Colorado, and the big steps forward he's taken in 2016.
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Here are Arenado's slugging percentages over the four years of his big league career:
2013 -- .405
2014 -- .500
2015 -- .575
2016 -- .651
Here are his outside-the-zone swing percentages over those same four years:
2013 -- 41.6
2014 -- 38.0
2015 -- 38.5
2016 -- 31.3
These two things are inextricably related. As Statcast™showed earlier this year, the absolute worst thing a hitter who isn't Vladimir Guerrero can do is to make contact outside the strike zone. Last year, the exit-velocity difference between contact in and out of the zone was 8.2 mph; the slugging difference was 239 points. Last year, Arenado hit .342 on pitches in the zone and .226 on pitches outside it, which is completely unsurprising -- of course it's harder to square up lousy pitches.
Gif: Arenado HR
So the way for Arenado to improve, apparently, has been simple: Swing at fewer of those pitches. It's not only how he gets better pitches to hit, but how he's managed to turn his plate discipline stats upside down:
2014-15 -- 5.2-percent walk rate, 14.8-percent strikeout rate
2016 -- 9.4-percent walk rate, 9.4-percent strikeout rate
That's not a typo. Arenado has 11 home runs, he's struck out 11 times and he has 11 walks. Of the 20 times in Rockies history that the club has had a 35-homer hitter (which Arenado is well on pace to be), only twice has that hitter walked more than they struck out (Larry Walker in 1999 and Todd Helton in 2000).
Now, it's fair to note that Arenado is swinging less frequently at pitches in the zone, too, which is generally less than ideal. But look at what's happened with this new-found plate discipline -- his batted balls are working a whole lot harder for him.
2014
Fly-ball percentage -- 41.8
HR/FB -- 11.4 percent
Popups per fly -- 15.2 percent
Pull percentage -- 45.3
2015
Fly-ball percentage -- 43.9
HR/FB -- 18.5 percent
Popups per fly -- 10.6 percent
Pull percentage -- 45.6
Exit velocity -- 91.6 mph
Average distance -- 235 feet
2016
Fly-ball percentage -- 53.2
HR/FB -- 22.0 percent
Popups per fly -- 8.0 percent
Pull percentage -- 47.4
Exit velocity -- 93.3 mph
Average distance -- 253.5 feet
Gif: Nolan Arenado HR
Arenado has hit more balls in the air each year, and he's hit fewer of those for popups -- which are basically strikeouts, considering how poorly the success rate is for hitters on popups. And in the two years we have Statcast™ to measure with, Arenado has hit the ball harder and farther.
Now take all of that and notice that the balls Arenado is hitting harder and farther are increasingly to his pull side. That's a big deal, because last year, he was more productive to his pull side than anyone other than Kris Bryant, and he was just ahead Harper. Pulling the ball more is a good thing for Arenado, and you can get a sense of that by looking at where his 81 career home runs have landed -- almost exclusively in left or center field.

Arenado has even put some work into shaking the "Coors Field magic" myth, which was rightfully hung on him after 16 of his 18 homers in 2014 were hit in Denver. He's hit 53 since, and the split is nearly even, with 26 at home and 27 on the road.
Considering that Arenado also brings elite defense -- since 2014, he leads all third basemen in Defensive Runs Saved -- and only turned 25 last month, it's well past time to start talking about him the same way we do about Machado. It's not just about altitude. It's about tangible changes, at least in the small sample of the 2016 season to date. Arenado was a star last year -- and so far this year, he looks even better.