Threw this into the OP. Very important. So unless it's drastically different between hitter/pitcher, we can't just look at Hard%/BABIP and determine Hutch's BABIP has been higher because he has previously given up harder contact.
http://www.hardballtimes.com/offensive-batted-ball-statistics-and-their-optimal-uses/
So how can we use the BIS contact data?
Not for BABIP. This is seriously the wrong data to use if so-and-so has a low BABIP. Don’t say, “But he’s making hard contact (Hard%).” These stats do so very little to predict BABIP—in part because “hard contact” can be deep fly balls, and fly balls have the worst BABIP of all non-infield-pop-ups. And typically, weak or medium contact results in ground balls, and those have a higher BABIP. But ground balls can be hit hard too. Just stay away from BABIP with these stats.
For ISO and SLG variations. Is your team’s prized slugger no longer lashing doubles and homers? Check the BIS data. Major fluctuations there might indicate he’s declining. Otherwise, give it some time.
And to a degree, wRC+ variations. But a lot goes into a total-offense metric like wRC+. I’d be more inclined to look at a contact rate than a contact strength measurement. Contact is a clearly delineated event. Contact strength has a lot of noise. But in bigger samples, it can be useful. For instance: Nobody has even hit below 100 wRC+ when his Hard% is 35.5 percent or higher. In fact, very few hitters over 33 percent have been bad hitters—as a group, they average a 121 wRC+. Look at this:
[TABLE=width: 100%]
[TR]
[TH=bgcolor: #8E001C, colspan: 2, align: center]WRC+ BY HARD-HIT RATE QUARTILE[/TH]
[/TR]
[/TABLE]
[TABLE=class: sortable, width: 100%]
[TR]
[TD=bgcolor: #D4D4D4, align: center]Quartile[/TD]
[TD=bgcolor: #D4D4D4, align: center]wRC+[/TD]
[/TR]
[TR=bgcolor: #ffffff]
[TD=align: center]Max (43.2%)[/TD]
[TD=align: center]118[/TD]
[/TR]
[TR=bgcolor: #ffffff]
[TD=align: center]Q3 (31.4%)[/TD]
[TD=align: center]102[/TD]
[/TR]
[TR=bgcolor: #ffffff]
[TD=align: center]Q2 (27.8%)[/TD]
[TD=align: center]94[/TD]
[/TR]
[TR=bgcolor: #ffffff]
[TD=align: center]Q1 (24%)[/TD]
[TD=align: center]82[/TD]
[/TR]
[/TABLE]
So fellas hitting under 24 percent Hard-rate are probably not doing well. But remember: there’s a lot of volatility here. The standard deviation in that bottom quartile is 13.6—meaning about 68 percent of the data lies between 68 wRC+ and 96 wRC+. It’s a wide swath.
What it tells us:
Taken together, these stats can give us a good feel for a hitter’s style—especially when it comes to groundball or flyball tendencies. Andrew Koo found a few years ago that the Oakland Athletics were leaning heavily on flyball hitters—and doing so to great effect at the time. A hitter’s GB/FB ratio might very well inform us how a hitter will perform in given stadiums or against given pitchers. The problem with these data, though, is that we are far to quick to look at line drive percentage and make bigger conclusions.
We can’t use LD% to rationalize a BABIP. You know, good for Dee Gordon that he is setting a career high in LD% during the 2015 season. That’s no reason to think he can keep his BABIP above .400 or above his career norms. Change “Dee Gordon” to “Starlin Castro” and “2015” to “2014” and we will see why LD% is a fickle master.
We can’t use LD% to rationalize a wRC+. Yes DJ LeMahieu has an enormous LD%, but he had an even higher rate in 2013—back when he also had a 68 wRC+.