05 June 2015

How Has Miguel Gonzalez Gotten So Many Whiffs?

A swinging strike is, objectively, the best possible outcome for a pitcher. They account for most of the variation in his strikeout rate, which in turn accounts for most of the variation in his ERA. In the immortal words of Carson Cistulli, "...they're awesome to watch". Thus, when a pitcher dramatically increases his whiff rate, it generally means he'll pitch better overall.

By runs allowed, Miguel Gonzalez has done about as well in 2015 (89 ERA- in 68.2 innings) as he did in the years that preceded it (85 ERA- in 435.2 innings). That's a shame, because his present xFIP- of 100 beats his career mark by a wide margin. A higher strikeout rate has caused this improvement — he's punched out 20.8% of the batters he's faced, as opposed to 17.0% in the three seasons prior. The cause for this? You'll never guess:

Year Gonzalez SwStr% MLB SwStr% Gonzalez SwStr%+
2012 8.9% 9.3% 95
2013 8.2% 9.5% 87
2014 8.1% 9.6% 84
2015 10.5% 9.7% 108

Yes, Gonzalez owns a notably above-average rate of swinging strikes — higher than any other starter on Baltimore's staff. Most pitchers who struggle to top 90 don't post numbers like that; how has Gonzalez done it?

Well, he certainly hasn't used his fastball, since its whiff rate hasn't budged much from previous years. Instead, he's ridden a better slider and splitter to this success; we'll analyze each individually.

Let's start with the splitter. It's always possessed average velocity and movement, which is more than Gonzalez can say for his other pitches. He's also consistently blown it past opposing hitters, but to varying extents by year:

Its swing-and-miss rate has gone from phenomenal to very good to phenomenal again. (Per Eno Sarris, an "above average" splitter gets whiffs 16.3% of the time.)

Zone maps explain this variance. In its first sensational campaign, Gonzalez buried it in the dirt all the time:

He then began to elevate it slightly in the next two years...

...before returning to his original recipe this season:

Low splitters have always excelled for Gonzalez, accumulating many more swinging strikes than anything up in the zone; thus, he now relies on them much more. These pitches have brought him a lot of his overall success this season.

But, lest we forget, he's also bettered his slider, which has never dominated like it does currently:

What's behind this rise? While Gonzalez's slider actually has more velocity and movement than the MLB average, it's only begun to fulfill its potential this year. And as with his splitter, the difference here comes down to location. Through the first three years of his career, Gonzalez threw the splitter low:

He deceived hitters the best, however, when he moved it low and to the left — which he's therefore done much more often in year four:

Hence, the more effective slider, elevated to great heights by a lack of elevation.

As Baltimore's pitchers — chiefly their starters — have struggled somewhat out of the gate, Miguel Gonzalez has pitched better than ever before. Sure, he's sacrificed a lot of home runs, but once his HR/FB% regresses from its current 16.3% mark to something around 11-12%, his ERA could fall even further with it. In the past, he's proven that he can outperform his subpar peripherals to post solid results; if those peripherals become even average, we could see a star.


Berdj J. Rassam said...

Miguel is a very solid pitcher - any starting rotation would love to have him.

Matt Perez said...

Well done.