How Altuve became MLB's unlikeliest slugger

The first thing you think of when you think of Houston's Jose Altuve is, "He's only 5-foot-6." Fair or unfair, baseball's most diminutive player will always have that label, if only due to never-ending pictures like this. That's been the Altuve story for most of his career: He's short, he's fast and he gets by because he hits for a high average.
That's all true! But there's also a new angle to the Altuve narrative, one that you probably never saw coming: He's also now a power hitter who has as many homers (nine) as Chris Davis or Josh Donaldson, and more than Albert Pujols, Paul Goldschmidt or Mike Trout. Altuve's 190 Weighted Runs Created Plus is second best in all of baseball, behind only David Ortiz. Small stature or not, he's crushing baseballs like the most elite hitters in the game, and it's turned him into a superstar.
• Cast your Esurance All-Star ballot for Altuve and other #ASGWorthy players
Let's grant that it's still only May 16 and it's unlikely that Altuve will maintain this pace and end up with 36 home runs. That said, this is another step in his continued offensive evolution, because this is the third iteration of Altuve, who somehow only turned 26 earlier this month.
Gif: Jose Altuve homer
The three Altuves we've seen, to date:
2011-13: Decent player made to look better by a struggling team (91 wRC+, 2.3 WAR)
We intend no disrespect there, but it's basically true. As the 2011-13 Astros were losing 324 games, Altuve became an All-Star in part because every team had to have representation, and there just weren't a lot of Houston alternatives at the time. Since a 100 wRC+ is set as "league average," Altuve's first few years were below average, and it was worth wondering at the time whether he could be a starter on a contending team, or just one that was scrambling to put a lineup on the field.
2014-15: Improving player on an improving team (127 wRC+, 9.1 WAR)
Altuve made big steps forward as his team rebounded from the basement and won the 2015 American League Wild Card Game, cutting his strikeout percentage from 12 percent to 8 percent and adding power, increasing his slugging percentage from .377 in his first three years to .456. Even before 2016 began, there was an argument to be made that Altuve had improved so much that he could be called baseball's best second baseman, as I did in an MLB Network Top 10 ranking in January.
2016: Superstar power hitter and elite performer (190 wRC+, 2.7 WAR)
For reference as to what a 190 wRC+ really means, beyond being "90 percentage points better than league average," note that when Bryce Harper had a historically great year in 2015, he did so with a 197 wRC+. So while Altuve isn't quite likely to keep that up, this isn't just a small sample thing, given both his continued improvement and surprising youth -- he's younger than Giancarlo Stanton, Jackie Bradley Jr., Eric Hosmer and Starling Marte.
Gif: Altuve homers against SEA
So how exactly has a player like Altuve added such a powerful new dimension to his game? You can't crush baseballs with the bat on your shoulder, and yet that's been a key to Altuve's improvement: He's swinging far less. Let's keep it simple and boil this down to three key takeaways:
1. Altuve has become extremely selective in the pitches he swings at.

2. He has been hitting the balls he makes contact with harder.
   
3. Altuve has been hitting those balls at a much more ideal launch angle.
   There's no questioning that first item. Over the past two years, Altuve went after nearly 52 percent of the pitches he saw. This year, that's down to 41 percent, and more importantly, his chase rate -- percentage of swings at pitches outside the zone -- has fallen from 38 percent to 25 percent. That's directly related to how Altuve's walk rate has nearly tripled (he has 22 walks in 179 plate appearances this year after 33 in 689 plate appearances last year), which is crucial for a fast player who routinely steals over 30 bases.
   But as we've learned, avoiding contact at bad pitches is directly related to increased Statcast™ exit velocity, and few hitters have had a higher year-to-year exit velocity increase than Altuve, who has gone from an 86.1 mph exit velocity in 2015 to 90 mph this year.
   It's not just about hitting the ball hard, either. Consider batted balls over 100 mph at a launch angle between 10 and 35 degrees, a combination that has led to a Major League total average of .776 and a slugging percentage of 1.944 in the Statcast™ era, which is to say it's a really, really good thing for a hitter to do. Last year, 5.7 percent of Altuve's batted balls fit that description. This year? It's nearly tripled to 15.3 percent, and Altuve hits .816 on those kind of balls.
   There's also evidence that Altuve has opened his stance, which makes sense, given where his home runs tend to end up. (Altuve pulled the ball 35 percent of the time in 2012-13, and 44 percent since.)
   
   So what you have here is a player with all the indicators pointed in the right direction. Always a baserunning threat -- his 177 steals since 2011 tops Dee Gordon by seven for baseball's highest total -- Altuve has improved his defense, his plate discipline, and now his power. He's no longer "a good hitter for his size." He's just "a good hitter," and one of baseball's elite players. In what's been a rough start to a promising Houston season, at least there's this. Altuve is a superstar.