If you had been told before the season started that a Major League starting pitcher was going to make a run at posting the best HR/FB ratio in the last 12 years, Chacin might have been one of the very last people you took. Joe Blanton probably would have been the very last, but Chacin would have been standing around looking at Blanton when everyone took their final picks. And yet, here we are, and after 19 starts, he’s allowed just three home runs. Kelvin Herrera gave up as many home runs in one appearance — which lasted 2/3 of an inning and involved him facing six batters — as Chacin has while facing 493 batters all year.
In the UZR Era (2002-2013), the record for HR/FB is 3.7 percent, set by Matt Cain two years ago. You probably remember that the key to Matt Cain's consistently low ERA's has been good luck, an inscrutable ability to keep fly balls from flying over fences, or some combination thereof (you choose).
In fact, Cain's the only pitcher from 2002-2012 with a figure below 4 percent.
Chacin's figure this season is below 3 percent. Which does seem quite notable.
Now, a word about meaning ...
The past meaning is obvious: Chacin's got a 3.53 ERA this season; with a normal HR/FB percentage, it would be roughly half a run higher. Lower than I expected, actually. The past meaning isn't zero, but it's hardly notable.
The future meaning is almost as obvious: There isn't any. From this moment through the end of his career, Chacin will probably give up home runs on roughly 10 percent of his fly balls, except a tick or two higher while he's a Rocky. Because of Coors Field, which (as Dave points out) remains a homer-happy ballpark, even with the humidor.
There's a deeper meaning here, though. Jhoulys Chacin has given up exactly three home runs in exactly 120 innings, which is easily surprising enough to reaffirm, yet again, our abiding faith in the wonders of baseball randomness.
Many of us would like to count everything ... while reveling in the fact that counting everything still won't allow us to predict everything.