Cubs rookie David Bote has only been in the Majors long enough to accumulate 139 plate appearances this season, fewer than a dozen of his Chicago teammates, and fewer than nearly 400 other hitters in the big leagues. For a former 18th-round pick who's been up and down between the Majors and Minors five times this year, you wouldn't think you could learn very much from 139 times to the plate scattered over five months.
But Bote has made the most of his time filling in for Kristopher Bryant, mostly by coming up big in huge spots. There was his two-out, down-three walk-off grand slam with two outs to beat Washington on national television on Aug. 12, and there was the walk-off home run to beat Cincinnati last Friday. There's the fact that five of Bote's six homers have either tied the game or given the Cubs the lead. On a Chicago team not lacking for stars or heroes, Bote (.267/.345/.475) is already becoming something of a fan favorite.
That's all a nice enough story, so far as seeing some big league success from a graduate of a small Kansas community college who never appeared highly on any top prospect lists goes. But where does it go from here? Are we seeing the beginnings of the next valuable member of the Cubs' lineup? Or simply the next Bryan LaHair?
We can't know the answer to that yet, of course, but even in his limited time in the bigs, we've learned something very important about Bote: He hits the ball really, really hard -- hard enough that he's at or near the top of some pretty important exit velocity leaderboards. (While "exit velocity" is a new term, it measures something extremely simple: How hard did the batter hit the ball?)
Hitting the ball hard doesn't by itself make you a star, but it is a skill, one that not everyone has, and there's a pretty strong correlation between hard-hit balls and success. 

Let's start with the average exit velocity leaders, looking at the 444 hitters with at least 50 batted balls so far this year. You're going to recognize the names here. You're also going to notice Bote.
Average exit velocity leaders in 2018, minimum 50 batted balls
95.8 mph -- Aaron Judge, Yankees
94.5 mph -- Bote, Cubs
94.4 mph -- Giancarlo Stanton, Yankees
94.4 mph -- Nelson Cruz, Mariners
94.3 mph -- Jose Cabrera, Tigers
You can't fake your way onto a list with those names. Among the next 10 names: Joey Gallo, J.D. Martinez, Matt Olson and Khris Davis. If you're on that list, you crush the ball. (Obviously: You have to make contact in the first place, and it's better to hit the ball in the air. We'll get to that; for now, let's focus on the hard-hit skill.)
Another, perhaps preferable way to look at this is to look at "hard-hit rate," which we define the number of balls hit with at least 95 mph of exit velocity. This often works better than an "average" number, because while hitting a ball at 40 mph or 60 mph or 80 mph will affect your average, it won't affect your success rate much. They're just different flavors of weak contact. At 95 mph of exit velocity is where it really starts to "matter," so the more balls you can hit that hard or harder, the better. 
Looking again at the same 444 players with 50 batted balls, this time sorted by hard-hit rate, Bote doesn't just rank well. He ranks at the top.
Hard-hit rate leaders in 2018, minimum 50 batted balls
56.8 percent -- Bote, Cubs
56.3 percent -- Judge, Yankees
54.6 percent -- Kendrys Morales, Blue Jays
54.2 percent -- Martinez, Red Sox
53.8 percent -- Ryan Zimmerman, Nationals
At the bottom of the list: light-hitting speedsters Ronald Torreyes (10.3 percent) and Billy Hamilton (7.7 percent). These numbers all align with the eye test pretty well.

It's pretty clear that this is measuring a skill, one that Bote has. And furthermore, it's clear that it's a pretty important one. Just look at the extreme differences in success across the Majors this year when a ball is hard-hit -- at 95 mph of exit velocity or more -- compared to when it's not.
Hard-hit balls (95 mph -plus exit velocity) in MLB in 2018
.523 average / 1.044 slugging
Weak-hit balls (below 95 mph exit velocity) in MLB in 2018
.220 average / .259 slugging 
Over 96 percent of home runs are "hard-hit," and nearly 80 percent of extra-base hits are "hard-hit." This is all intuitive, really; if you've seen baseball, you know it's better to hit the ball hard. This is merely putting numbers to what your eyes already told you, and if your eyes were telling you that the ball jumps off of Bote's bat with a lot of life, you'd be correct.
Bote has hit it so hard, in fact, that he's got five balls hit at 110 mph or more, only one fewer than Paul Goldschmidt in a fraction of the plate appearances -- more than sluggers like Mike Moustakas, Edwin Encarnacion, Michael Conforto, Charlie Blackmon or Bryant.

So Bote hits it hard. It's good to hit it hard. Why, then, wasn't Bote ever a highly ranked prospect? Part of it was simply performance, obviously. He didn't slug higher than .384 in any of his first four pro seasons, totaling only 18 home runs. But part of it was also about approach. Bote's skill in hitting the ball hard didn't come out of nowhere, after all. It was the ability to translate it to game success that had to improve. Just look at the final line of this section of Bote's MLBPipeline scouting report from earlier this year:
"His strength and bat speed combine to give Bote more power than most middle infielders, and some of the highest exit velocities among Chicago farmhands. His home run surge came after he worked to add more loft to his right-handed stroke."
Bote had to add more loft, which is another way of saying that hitting the ball hard on the ground is nice, but hitting the ball hard in the air is where you make your money.
As The Athletic noted in a subscription-only article in April, Chicago's coaching staff knew that Bote could crush the ball in the Minors, but they needed to find the right way to get that information to him in a way that could be actionable, which they began to do last season.
"I had one of the highest exit velos in the organization, but with a really low launch angle," Bote said. "So they were saying if we could use that exit velo and get a little bit more launch angle."
None of this guarantees that Bote will be a star, obviously. On the other side of town, Daniel Palka of the White Sox also has an elite hard-hit rate, but he's struggled to make enough contact to make the most of it. Hitting the ball hard is a tool, just like fastball velocity is a tool. You need a lot more than that to succeed, but it's a tool you want to have. As Bote is proving, his ability to crush the ball is no fluke. It's a great sign of potential future success.