Posted Under: Stat of the Week
In the article on Earned Run Average Player Analysis, I referenced Felix Hernandez’s increase in Earned Run Average in 2011 to be linked to him giving up more fly balls than in previous years, as 11-12% of all fly balls in a season on average are home runs. Hernandez’s Ground Ball to Fly Ball (GB/FB) ratio dropped from 1.19 in 2010 to 1.02 in 2011, according to Baseball-Reference, which means the denominator, fly balls, increased to bring a ratio closer to 1 to 1. An important note is that Baseball-Reference’s GB/FB ratio counts line drives as fly balls which means its version of GB/FB includes every hit ball a pitcher allows, while other baseball database websites, such as FanGraphs, do not include line drives in its GB/FB ratio.
When baseball fans think of ground balls, they think of pitchers such as Derek Lowe, Chien-Ming Wang and Brandon Webb (circa 2006), guys who threw sinkerballs effectively and got hitters to get on top of the ball and hit grounders to their infielders. Another way to measure a pitcher’s ground ball proficiency is Ground ball% (GB%) which measures what percent of all batted balls a pitcher allows are grounders. According to FanGraphs, a pitcher who has a GB% of over 50% is considered a ground ball pitcher as the average GB% in MLB is usually around 44%. Lowe, Wang and Webb certainly fit the bill of ground ball pitchers as their career GB% were 62.5%, 59.5%, and 64.2%, respectively.
An appealing aspect of ground ball pitchers is that when comparing the different types of hits, ground balls, fly balls and line drives, ground balls are the least likely to lead to runs. According to Steve Slowinski of FanGraphs, ground balls produce 0.05 runs/out (R/O), while fly balls produce 0.13 R/O and line drives 1.26 R/O. This does not mean that ground ball pitchers will give up less runs than fly ball pitchers overall as Jered Weaver, who has established himself as one of the best pitchers in the American League, has a career GB% of 33.3% and a career GB/FB ratio of 0.51, meaning he gives up 2 fly balls to every ground ball according to Baseball-Reference.
Further, ground ball pitchers do not record as many strikeouts on average, as they typically pitch to contact in order to be effective, which can be a disadvantage as strikeouts allow pitchers to set down a batter and not worry about external factors like luck or the defense behind them (which if you remember are factors taken out when looking at a pitcher’s Fielding Independent Pitching). It is important for front offices to know the tendencies of their pitchers and build the right defense behind them. Weaver has benefited from an outfield with a lot of range, basically having three centerfielders playing behind him, while ground ball pitchers should have a strong infield defense behind them, similar to the defense C.J Wilson (49.3 GB%) had with the Texas Rangers who had Adrian Beltre, Elvis Andrus and Ian Kinsler, backing him up.
Check back Thursday where we’ll evaluate the rise of Brandon McCarthy and look at the Cleveland Indians which have a pitching rotation dominated by ground ball pitchers.