Last year, at age 22 in his rookie season, Jhoulys Chacin pitched 137.1 pretty good innings to a line of a 3.28/3.54/3.62 ERA/FIP/xFIP. Those are all pretty solid numbers, though his pitching at Coors Field might give a fantasy player a little worry that he is unlikely to perform to his peripherals in the future—or, as in the case of 2010, to put up a better ERA than should be expected.
Now, this year, Chacin’s numbers have changed in some very interesting ways. His ERA is near identical to last year (3.33), but his xFIP has dropped from a fairly solid 3.62 to a really good 3.17 (his FIP has risen thanks to some bad home run luck). More interesting is how this change has occurred: Chacin’s strikeout rate has declined, but the decline has been compensated for by a decrease in his walk rate and a large increase in his ground ball rate. Whereas previously Chacin relied on his strikeout ability (along with an average ground ball rate) to get outs, he has increasingly been able to rely upon the ground ball this year to get outs.
And for a pitcher in Colorado, that’s a pretty good thing to be able to rely on.
But the question is: Is this sudden groundball ability REAL? Or is it just a mirage, a fluke of a small sample size? Lets look at his pitches in search of an answer.
Chacin appears to have five pitches: a four-seam fastball that has a lot of cut, a sinking fastball (two-seam probably) without much tailing action, a change-up, a curveball, and a slider. The movement and velocity of these two pitches each of the last two years can be seen below*:
|Pitch Type||Year||Pitch Velocity (MPH)||Horizontal Movement||Vertical Movement|
*The two fastballs are not super-clearly distinguishable via PITCHf/x and the two breaking balls (the curve and the slider) aren’t either. However, I’m pretty sure that my classifications are for the most part correct.
As you can see, there have been barely any change in the movement or velocity of any of Chacin’s five pitches. Really, all of the changes in velocity/movement you see in the chart above are within the PITCHf/x system’s margin of error.
This suggests, of course, that the change in Chacin’s results is probably not caused by a change in the movement of his pitches.
The mysterious increase in ground balls
So the question is: Where has the increase in ground balls been coming from? The ground balls appear to be coming from Chacin’s two fastballs, especially against left-handed batters. Check out the GB rates on Chacin’s fastballs each of the last two years:
Four-seamer in 2010: 43.6%
Four-seamer in 2011: 71.9%
Sinker in 2010: 44.4%
Sinker in 2011: 67.5%
Four-seamer in 2010: 40.7%
Four-seamer in 2011: 61.8%
Sinker in 2010: 57.14%
Sinker in 2011: 52.38%
As you can see, the groundball rates have gone up pretty dramatically on these pitches to lefties, and they’ve gone up on the four-seamer to right-handed batters as well. Now the fact that Chacin, a right-handed pitcher, might get a decent GB rate against left-handed batters (and a better rate than against right-handed batter), is not surprising. Chacin uses a fastball with a lot of cut, which tends to result in reverse groundball splits—the pitcher gets good GBs against opposite-handed batters (lefties in this case). In addition, Chacin’s pitches to left-handed batters (more than 50 percent of the batters he faces), are near always aimed on the outside part of the plate, the best part of the plate to get ground balls. So a decent GB rate on these pitches against left handers (even on the “sinker,” which doesn’t have the same cut) shouldn’t be totally surprising.
But at the same time there’s nothing in the way these pitches have been thrown against left-handed batters to explain why the GB rate should have increased so much this year. The pitches are being located in the same part of the strike zone, have basically the same movement, and the distribution of these pitches has basically remained unchanged. While perhaps last year’s GB numbers were lower than we might have expected, the increase we see this year is a bit much for us to simply explain it as regression from bad luck last year.
In fact, it appears that the groundball rate increase this year against left-handed batters is simply caused by good luck. Last year on the four-seamers, Chacin would give up non-ground-balls on pitches in the middle to inside part of the plate. This year, despite mostlyseeing his pitches in the same area, batters have not put these middle-of-the-plate to inside pitches into play at all. I would suspect this trend not to continue.
Now there are several possible explanations for the GB increase. First, Chacin is locating more of his pitches within the strike zone this year. Perhaps this is resulting in an overall increase in GB rates? I’m not sure why it would, and the GB rate change appears to be universal, on pitches both in and out of the strike zone. Second, Chacin has slightly changed his pitch usage from last year by throwing more curves and fewer change-ups. Perhaps this is affecting batters’ swinging habits so that they hit the fastballs more into the ground? Once again, I’m not sure why that would have this effect either.
Finally, the four-seamers do seem to have about a half inch more cut on them than they did last year. However, as noted above, this change is basically within the PITCHf/x system’s margin for error, and I hesitate to claim it as real and the cause for any change in results.
Against right-handed batters, it appears that there is one additional change: The four-seam fastballs are being aimed a little bit more outside than last year, which would make us expect a few more ground balls (we don’t see this change in the sinkers, whose gbroundball rates have remained basically constant this year from last year). So perhaps the GB rate increase is sustainable against these batters.
There is one change to Chacin’s pitching that is briefly mentioned above: He is throwing more pitches in the strike zone than last year against both right and left-handed batters. This is an easy explanation for how Chacin has managed to reduce his walk rate this year. So this improvement by Chacin should be sustainable (as long as he can keep up the greater “accuracy.”)
Chacin has been very impressive this year. However, at least some of his improvements this year are bound to regress, particularly the improvement of his GB rate against left-handed batters. It wouldn’t be surprising for him to end up with a groundball rate higher than last year’s against such batters, but it should be closer to last year’s rate than this year’s really great rate. Against right-handed batters, his GB rate may also regress.
Chacin’s improved walk rate should remain the same, but signs also point to his decreased strikeout rate continuing as well (presumably because, with fewer pitches being out of the strike zone, batters are less likely to miss when they swing).
The result is that Chacin’s peripherals should get worse as the year goes on, and I doubt he’ll continue to put up better peripherals and overall numbers than last year for the rest of the season.