MLB: Proposing a New Metric to Evaluate Hitters

Statcast gives us the tools to determine which MLB hitters are best at the process of hitting, so there should be a metric that takes advantage of Statcast’s data.

Detroit Tigers third baseman Nick Castellanos is making a great argument for the creation of a new statistic to evaluate MLB hitters.

Check out this video of Castellano’s home run and I’ll explain.

According to MLB’s Statcast, that home run, which came in game one of a doubleheader against the Chicago White Sox, had an exit velocity of 105.35 mph at an angle of 25.06 degrees. Taken separately, neither exit velocity nor launch angle means a whole lot. But take a look at the interplay of those two numbers, and suddenly they mean a whole lot more.

My first exposure to the concept of a new metric came from this awesome post by Rob Arthur at FiveThirtyEight. In it, he outlines the value of batted balls based on both exit velocity and launch angle, not one or the other. Naturally, well-hit balls (an exit velocity over 90 mph) hit at advantageous angles (between 10 and 40 degrees) have much more value than ground balls and fly balls that are hit at high angles or without enough velocity.

My true moment of enlightenment came when I read this deliciously insightful post by August Fagerstom of Fangraphs. In it he outlines how in the future Statcast could give us the ability to evaluate hitters based on the process of hitting the ball, not the results — think Fielding Independent Pitching but for hitters. Just like weighted on-base average, Wins Above Replacement and weighted runs created plus (wRC+) don’t treat singles, doubles and walks equally, a new metric wouldn’t have to treat each single equally, either.

These two posts and perusing Baseball Savant’s Statcast data got me thinking: Okay, so who is best at this process? To check, I did a search for the batters who have hit the most batted balls with an exit velocity over 90 mph and a launch angle between 10 and 40 degrees. Here are the top 10 (all stats entering Sunday):

Not surprisingly, some of the best hitters in the game crack the top 10 — and holy cow, there are three Tigers! But to be perfectly honest, I didn’t expect to see Castellanos at the top.

It’s abundantly clear Castellanos got better at the process of hitting. In 2015 Castellanos had a 98 OPS+. He was basically average. He wasn’t going to earn any accolades with that type of offensive production, but this season he’s hitting a career best  .297/.336/.525 with 18 home runs after Sunday’s double dip.

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Or, to put it in another way, Castellanos got better at hitting the ball harder and at a better angle. For some perspective, last season Castellanos hit 102 balls that fit the above mentioned parameters; he’d already hit 106 entering Sunday.

But the parameters of the search above exclude a lot of batted balls with an above average run value. (In Arthur’s article, look at the band of balls with launch angles between 10 and 25 degrees and exit velocities between 60 and 85 mph.) So I did another search with those parameters, and lo and behold, Castellanos was eighth in MLB with 14 batted balls in that range.

Keep in mind, this is based on a partial season’s worth of data and the results are hardly conclusive. For example, if the table above showed the top 200 players instead of the top 10, Milwaukee Brewers outfielder Ryan Braun (135 OPS+ entering Sunday) would be 147^th; Chicago Cubs outfielder Dexter Fowler (141) would be 161^st; and Miami Marlins outfielder Giancarlo Stanton, the king of Statcast exit velocity, would be 164^th.

But how incredible would it be if there was a metric to show which players were best at the process of hitting? Based on the two searches above, Castellanos would be near the top, which seems so counter-intuitive that it could be revolutionary to the way we analyze the game; it wouldn’t be the first time Statcast has changed our view.

Next: Bregman Headed to the Big Leagues

So I’m going to propose the creation of a new metric — by someone much smarter than me and with the skills to do so — that measures the percentage of a hitter’s batted balls that have an above average run value. (To be fair, I have seen some more narrow versions of such a metric.) In fact, it doesn’t even have to be above average run value; wOBA, wRC+, OPS+ or any other number could be used as well. We can call it Barrel Factor, or Sweet Spot Percentage or some other dopey name, but this type of ranking system would open our eyes.