Scherzer’s Sliders

Max Scherzer has looked pretty good in his first ever postseason. He’s flashed some serious heat — bumping his fastball as high as 99 mph in his relief appearance last week — but there’s another pitch that’s been quietly killing opposing batters: his slider.

Despite being thrown less often in the past two seasons than his four-seam fastball and his changeup, Scherzer’s slider is his best pitch when it comes to inducing swinging strikes. On a per-swing basis, the swinging-strike percentage is right around 40%, going back to 2010. The league average for sliders is 33%. And there’s more, when it comes to Scherzer’s slide-piece: looking at the pitch more closely, we can see that it’s undergone a significant transformation since the beginning of this year:

His slider’s velocity was reasonably consistent during the 2010 season, but since April of this year, it’s been on the way up.

An uptick in Scherzer’s fastball velocity explains some of this, but looking at the difference between his fastball velocity and his slider velocity on a game-by-game basis shows that his slider really is acting as a different kind of pitch:

So what does this mean? The simplest way to determine whether the velocity increase has done anything to boost the slider’s effectiveness it to examine whiff rates over the pitch’s different phases. For now, I’ll split it into the 2010 season (phase one), April 2 through June 6 (phase two) and June 11 to the end of the regular season (phase three). My cutoffs are based on notable velocity differences from one period to the next. Using this measure, the hard slider is definitely the way to go:

         mph      Swings   Whiff%
1        84.0     221      41%
2        80.2     108      21%
3        84.2     189      44%

He’s already started throwing a few extra sliders from last year (18% in 2011 up from 15% in 2010), and the hard version of the pitch looks like a nice weapon for him.

It’s worth noting that Scherzer is a big fan of sabermetrics and PITCHf/x, so he is probably attuned to this information.