Zach Britton, the superb left-handed closer for the Orioles, was a mediocre starter from 2011 until 2013. Upon becoming a reliever in 2014, his fastball velocity jumped up by 3-4 mph and he was immediately excellent (ERA 1.65/ERA+ 240). He repeated his excellence in 2015 (ERA 1.92/ERA+ 215), and then in 2016 blew mere excellence out of the water with a ridiculous ERA of 0.54 (ERA+ of 827!) and a WHIP of 0.836, leading the league with 47 saves.
The sinker is thrown very hard, averaging about 96.7 mph (the third-fastest fastball among left-handed pitchers) and maxing out at 100.0 mph. Normally fastballs — especially very fast fastballs — are thrown with a lot of backspin, which makes the pitch “rise” (that is, it ends up higher than it would if it followed the course of gravity alone). Sinkers, like Britton’s, attempt to minimize backspin so that there is less rise. Britton does this very effectively; if we look at the left-handed pitchers whose fastballs average mid-90s or higher, all have far more vertical movement than Britton’s sinker (the red dot on the charts below):
This exceptional “sink” (relative to expectations) causes batters to swing and miss, or very often make weak contact on the top of the ball and ground out — Britton’s groundball rate of about 78.3% on his fastball is far higher than the overall average of about 51.3% on sinkers thrown by other pitchers.
Pitch usage and trends. Britton’s main pitch by far is his sinker (“FT”), which made up 92.4% of his pitches in 2016; the remaining 7.6% were sliders/curves (“SL”). He uses the slider more often to left-handed batters, and almost entirely when ahead in the count; in 2-0, 2-1, 3-0, and 3-1 counts, he threw no sliders at all in 2016:
His repertoire and usage remained consistent over the season. With many of his appearances being short (only seven of his 69 appearances were for more than one inning; he averaged just 15 pitches per game), his slider only appears sporadically:
Pitch value. Both of Britton’s pitches are well above average in terms of total bases yielded per 100 pitches, with his sinker being elite, and handle both right- and left-handed batters equally well. His sinker is also about average in terms of balls per 100 pitches, but his slider is considerably worse than average in that regard, especially to left-handed batters:
Pitch location. Britton’s sinker, unsurprisingly, mainly targets the very bottom of the strike zone, although he does use the whole bottom half of the zone. His rare sliders often end up below the strike zone — down and in to right-handed batters, down and outside to lefties: