Feb 16, 2012

How To Evaluate Pitcher Strikeout Totals




After previously talking about evaluating ERA, it's time to turn our eyes to the always sexy strikeouts. For fantasy purposes, you'll rarely make a huge investment in a pitcher unless he can strike people out early and often. Being able to accurately predict whether a pitcher will repeat his strikeout totals is an important part of being a good fantasy baseball manager. Unlike ERA or WHIP, there is nobody else behind the pitcher that plays a role in the strikeout so we need to really evaluate the pitcher's skillset in order to evaluate his strikeouts.
Strikeouts
A pitcher's strikeout rate is actually a relatively stable statistic. Unlike ERA which can vary quite a bit from year to year, a pitcher who strikes people out usually will continue to do it each year. However, there are always some cases which are worthy of further investigation. For instance, Zack Greinke had a 7.40 K/9 rate in 2010 but then a 10.54 K/9 in 2011 so you may wonder who the real Greinke is which would require a deeper look at his skills. Our best friend in evaluating strikeout potential comes via the PitchFX data that is available through a variety of sources but originates from Brooks Baseball. This data allows us to evaluate a multitude of things from pitch speed, pitch angle to pitch location and also shows us how often pitch were hit or not. In evaluating strikeouts, we're mainly interested in how often a pitcher can make a batter miss the pitch.

Swinging Strike Percentage (Sw-Str%) is a good starting place for that. As the name suggests, this looks at the percentage of pitches that the batter swings at but misses from the pitcher. Pitchers who are more skilled at striking batters out will have a higher Sw-Str%. For reference, the league average is generally between 8% to 9%. So, if you see a pitcher well above or below that mark then you can expect his strikeout totals to also be above or below that mark. If you see these rates going up or down over a pitcher's career then it may be cause for further investigation.

Contact Percentage (Contact%) is where my eyes would wander to after Sw-Str%. Once again, the name is pretty self explanatory but it is the percentage of swings that a batter makes contact with the pitch. Along the same lines, Zone Contact Percentage (Z-Contact%) tells an interesting story in this regard too as it is the percentage of swings at pitches in the strike zone that are made contact with. An average pitcher will have a Contact% around 80% or Z-Contact% in the high-80's. When a pitcher is able to create a lower Contact% then he is showing evidence of being a better strikeout pitcher.

These three numbers above correlate well with strikeout rates in a given year. So, if you see a pitcher early in the year with a great strikeout rate but low Sw-Str% and/or high Contact% then you can make the assumption that his great strikeout rate will not continue.

As another check for strikeout prowess, looking at a pitcher's Velocity can be handy as well. This becomes especially important when you see a drop in strikeout numbers because a drop in velocity as well can mean that the pitcher is suffering through a physical injury (or perhaps showing signs of age).

If you really want to dig deep into a pitcher's ability and mindset, there's even data available on the value of his pitch types (curveball, slider, fastball) and how often the pitcher is throwing each and that might tip you off to a change in a pitcher's strategy. A strikeout rate could suddenly bloom when a pitcher stops throwing one of his bad pitches and starts throwing his better pitches more often, for instance.

One thing to keep in mind that can affect strikeouts in an unexpected way is Batting Average on Balls in Play (BABIP). When a pitcher has a very high BABIP, he is getting unlucky as more balls are falling in for hits. This affects strikeouts because that means that he gets another chance for a strikeout instead of that ball hit into play becoming an out like it possibly should have. A pitcher with a lower BABIP may end up showing a reduced strikeout total for the opposite reasons.

All of this data is available on the player pages at Fangraphs, if you scroll down far enough. So, there you have it! You can officially make a solid evaluation of a pitcher's strikeout rates to have an idea of whether they'll remain stable or not. You go, you!

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