March 14, 2013 posted by Matthew Dewoskin

Stats You Should Know: O-swing % Edition

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Josh Hamilton, OF, Los Angeles Angels

There’s a reason that “O-swing %” is filed under plate discipline stats at FanGraphs. It’s a good measure of plate discipline for a hitter and how good a pitcher is at making hitters forget plate discipline.

Simply put, O-swing % measures how often a hitter swings at pitches outside the strike zone. To calculate for hitters, simply divide the number of swings outside the strike zone by number of total pitches seen outside the strike zone.

It works a little differently for pitchers. For pitchers, it works as a “Fooled Ya!”-o-meter. This is totally different from the old school “Shawon-o-meter,” that stupid fans used to display in Wrigley Field whenever Shawon Dunston would get a hit. O-swing % tells us how often a pitcher is able to get a hitter to offer at something outside of the zone.

Generally speaking, fantasy GMs should want this number to be as low as possible for hitters and as high as possible for pitchers, but there are always exceptions.

Josh Hamilton has gotten more and more reckless every year he’s been in the league. He’s seen his O-swing % rise from 26.9% as a rookie in 2007 to 45.4% last year. This shouldn’t be that big of a deal for a guy with the bat speed of Hamilton, but what happens as he ages as his bat slow down? His O-contact %, the rate at which he makes contact with pitches outside the zone, has remained within a standard deviation or two of his 57.2% career average, but last year was the first time he dipped below 54%. If Hamilton starts to entire the decline phase of his career, it will start with an O-contact under 50% and an O-swing % in the 40% range. Fantasy GMs should want Hamilton swinging the bat because the baseball tends to go very far when he makes contact. As long as he still has the skills, it’s absolutely acceptable for a guy like Hamilton to swing away, but it is a trend that could cause trouble as Hamilton ages. 

Josh Willingham has also gotten more reckless in his middle-age. Willingham owns a career O-swing % of 19.4%, but his O-swing % shot up to 21.7% last year! Stop the presses! Do they still have presses anymore? Stop twitter! Willingham has one of the best batter’s eyes in the game today. There haven’t been a lot of guys to come along with Willingham’s ability to stay away from pitches outside the zone AND post a 35 homer season. Willingham only swung at 40.4% of all pitches he saw last year. Compare that to the 58.9% that Hamilton posted and you’ve got guys at total opposites of the hitting spectrum. The only difference is that Willingham will still be useful as he ages. The batter’s eye is usually maintained into the twilight of a hitter’s career. The immortal Frank Thomas posted a 13.8% O-swing % in his final year and he played that season without ankles. Willingham will be able to find a job with a major league team as long as 1. the league keeps the DH rule and 2. Willingham has eyes.

Want to know one of the oddest stats of the 2012 season? Bruce Chen lead all pitchers with a 35.2% O-swing %. Bruce effing Chen. He finished higher than Justin Verlander (35.0%), Cole Hamels (also 35.0%) and Jeff Samardjiza (34.2%). Actually, he finished higher than everyone who qualified. Chen’s career average is only 26.8% and that’s skewed by a few years spent in the bullpen. Chen doesn’t have imposing stuff, but he was somehow able to bait hitters into offering at pitches out of the zone. Verlander hasn’t had a season under 30% since 2007. It’s just another reason why Verlander is elite and what makes Chen’s 2012 results all the more surprising. He absolutely looks like the outlier in this data set.

At the other end of the spectrum is Ubaldo Jimenez and his 23.2 % O-swing %. Yeah, Ubaldo? You’re not fooling anyone anymore. Remember when you were awesome and posted a 29.2% O-swing with a 8.69 K/9? 2010 feels like it was 15 years ago. Almost all of Ubaldo’s swing metrics are headed in the wrong direction. There’s a completely reasonable chance that he’s out of American baseball by the time he’s 31 if he continues to deteriorate.

Edinson Volquez was also near the bottom of the O-swing table and it’s a little surprising. Volquez owned a 10.1% swinging strike % last year. The 26.0% mark was the lowest Volquez had posted since 2009 and he’s still capable of missing bats. He’s a solid bet to rebound a little in 2013.

O-swing % works in concert with the other plate discipline stats to provide a more accurate picture of what a hitter actually does at the plate. OBP is a useful stat, but it doesn’t really tell us how good a batter’s eye is or where he swings. The plate discipline metrics provide a much clearer picture and should be used to confirm suspicions.


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