Jake Arrieta’s Using His Sinker at (Maybe) Unsustainably High Rates

Looks like it’s time to add another weird trend to the list of odd Jake Arrieta observations. After a historical 2015 campaign, the bearded pitcher showed variable release points in 2016, which was associated with significantly less slider movement. As the 2016 campaign rolled along, the righty relied less and less on his slider.

As we’re seeing this season, he is leaning heavily on his sinker and is throwing the pitch exhaustively. In his last three starts, Arrieta threw a least 70 percent sinkers and decreased his curve rate by nearly 34 percent (numbers in chart represent percentages of total piches).

Game Fourseam  Sinker Slider Curve Change
PIT@CHN (7/8/17) 0 77.57 5.61 10.28 6.54
CHN@BAL (7/15/17) 0.99 77.23 7.92 10.89 2.97
SLN@CHN (7/21/17) 2.06 70.10 12.37 10.31 5.15
AVERAGE 4.74 58.35 13.43 15.64 7.85

But it’s not as if the reliance on sinkers is hurting Arrieta’s performance. He has a 2.95 ERA in those three starts and has only walked five batters (2.45 BB/9). Yet, if he continues with such a high dosage of sinkers, he could be in trouble because he has only generated only 15 percent whiffs — quite a difference from his ~25 percent norm — and has struck out only 12 men (5.89 K/9). Factoring in his decreased velocity makes me even more anxious.

It was highly publicized that Arrieta had been dealing with a blister or a skin issue on his thumb that stemmed back to spring training, so maybe this is why he isn’t throwing secondary pitches as often. Whatever the reason, we should monitor this trend, since a pitcher can’t rely on one pitch for more than 75 percent of their total offerings.

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