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Pounding the Zone: Walk Rate Peripherals

Posted By Eno Sarris On June 28, 2012 @ 10:30 am In Daily Graphings,Research | 5 Comments

When we look at a hitter that’s struggling to produce, we have plenty of peripherals at our disposal. When we look at a pitcher that’s struggling with his control, we have… two? We have his zone percentage, and we have his first-strike percentage. We can compare those to the league average and hope we have a sense of how important either is to his walk rate going forward.

Well, let’s see how well these things correlate to walk rate. Why not.

Seemingly, zone percentage is the most important number. You want to have a better walk rate? Throw the ball in the strike zone. Of course the two are related, but you might be surprised about the slope of the line describing their relationship:

Yeah that’s not a heck of a slope. The r-squared value for this relationship is .0875, meaning that zone percentage describes just short of 9% of the variance in walk rate. There’s a general relationship between the two, but this means that there are plenty of wild guys like Danys Baez in 2002, who hit the zone 56% of the time while walking 11.3%, and plenty of good control guys like Mark Buehrle last season, who hit the zone 43.1% of the time while walking 5.2% of the batters he faced. Zone percentage is just a general guide.

Why is this? It might be because pitchers with exceptional stuff can get batters to chase on pitches — that’s not a pitch in the strike zone, but it’s a strike, not a ball. Maybe we can find our low-zone-percentage, low-walk-rate hurlers and look at their o-swing percentage? Taking pitchers with a below-average zone percentage (we’ll use 49%) and an above-average walk percentage (we’ll use 8.5%), we get a group of 91 pitchers that averaged swings on 29.57% of their pitches outside the zone compared to the league average o-swing of 28.06%. But if you limit the list to only those with a better-than-average contact percentage, the list gets (smaller and) more interesting:

Season Name Zone% pfx BB% O-Swing% pfx Contact% pfx
2012 Stephen Strasburg 45.30% 6.40% 33.50% 71.90%
2012 Johan Santana 44.40% 8.50% 28.60% 73.20%
2010 Francisco Liriano 48.00% 7.20% 34.00% 73.50%
2012 Edwin Jackson 46.30% 7.00% 30.60% 74.40%
2012 CC Sabathia 48.10% 6.40% 34.00% 74.90%
2009 Ryan Dempster 46.70% 7.70% 31.50% 74.90%
2010 Tim Lincecum 48.50% 8.50% 31.10% 75.10%
2009 Tim Lincecum 49.00% 7.50% 30.30% 75.30%
2011 Mat Latos 48.00% 7.80% 31.30% 75.30%
2012 Dillon Gee 46.80% 6.60% 33.10% 75.60%
2011 Zack Greinke 45.80% 6.30% 29.80% 75.70%
2010 Shaun Marcum 48.70% 5.40% 33.80% 75.80%
2012 Shaun Marcum 47.50% 7.60% 31.10% 75.80%
2011 Matt Garza 48.10% 7.50% 33.90% 76.10%
2011 Chris Capuano 47.70% 6.60% 32.20% 76.50%
2010 Hiroki Kuroda 48.60% 5.90% 32.20% 76.60%
2011 Shaun Marcum 44.70% 6.90% 31.40% 76.60%
2011 Jaime Garcia 48.60% 6.10% 31.70% 76.70%
2008 Jake Peavy 48.30% 8.30% 28.90% 76.70%
2012 Gavin Floyd 48.50% 6.30% 29.20% 77.00%
2012 James Shields 46.40% 7.30% 34.20% 77.00%
2012 Matt Garza 48.70% 6.70% 30.30% 77.30%
2008 Brandon Webb 47.40% 6.90% 32.50% 77.30%
2009 Zack Greinke 48.10% 5.60% 30.30% 77.80%
2011 Hiroki Kuroda 47.80% 5.90% 30.90% 78.20%
2011 Yovani Gallardo 46.20% 6.80% 28.10% 78.50%
2010 Randy Wells 45.30% 7.50% 30.60% 78.50%
2012 Dan Haren 48.10% 5.50% 29.70% 78.70%
2012 Josh Johnson 46.10% 7.60% 28.90% 78.90%
2010 Wandy Rodriguez 46.80% 8.30% 29.90% 78.90%
2011 Dan Haren 47.60% 3.50% 34.10% 79.20%
2008 Derek Lowe 43.30% 5.30% 28.80% 79.20%
2012 Chad Billingsley 48.70% 8.20% 26.20% 79.20%
2012 Hiroki Kuroda 46.20% 7.60% 26.80% 79.30%
2009 Adam Wainwright 49.00% 6.80% 30.20% 79.40%
2011 Derek Lowe 36.90% 8.40% 31.10% 79.70%
2010 Johnny Cueto 48.80% 7.20% 27.70% 79.80%
2012 Felix Doubront 48.20% 7.80% 29.40% 80.20%
2011 Wandy Rodriguez 46.30% 8.50% 31.10% 80.20%
2010 Chris Carpenter 48.10% 6.50% 29.10% 80.30%
2010 Brett Myers 48.50% 7.10% 29.50% 80.30%
2010 Derek Lowe 37.80% 7.40% 31.10% 80.30%
2011 Tim Hudson 46.00% 6.30% 29.10% 80.40%
2008 Todd Wellemeyer 48.90% 7.70% 29.90% 80.40%
2012 Jon Lester 45.70% 6.70% 29.40% 80.50%
2012 Zack Greinke 43.80% 5.40% 28.80% 80.60%
Group Average 46.79% 6.93% 30.65% 77.56%
League Average 49.86% 8.48% 28.06% 80.66%

Now that we’ve narrowed our list to those pitchers that pitch in the zone less than average but still have better-than-average walk rates — and also garner more whiffs than average — we get a stronger result. These pitchers get whiffs on swings outside the zone, and that helps mute the effect of zone percentage on walk rate.

We still have first-strike rate to fall back on. It makes sense that fewer at-bats that start 0-1 will end up in a walk (4.6% vs the league average of 8.2%), but it also seems that if it was that easy, everyone would just throw strikes on their first pitch.

Here, the r-squared is .435, meaning that first-strike percentage is much more important to walk rate. It explains almost half of the variance in walk rate! That’s pretty impressive. After all those years hearing about the importance of getting strike one and pounding the zone — now we know which is more important.

As a bonus, the size of the circles in this last graph was determined by the pitcher’s zone percentage. As you can see, the bigger circles (better zone percentage) are clustered on the lower part of the graph. Perhaps, with the two together (and o-swing% and contact%?), we can find an equation for expected walk percentage. I’ll just have to go math up a little before we can get there.


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