# Deleting the Adjectives: Pitches per Plate Appearance

Something that separates a hardcore baseball fan and a casual baseball fan is appreciation for a good at-bat. While most of the focus is placed on the result of an at-bat, how they got to that result can sometimes be just as important.

Conventional wisdom says seeing more pitches in a plate appearance can often lead to getting that perfect pitch that a hitter can mash. It also drives up a pitcher’s pitch count, tiring him and, if done systemically, leading to an early exit for the pitcher.

But how much of an effect does a higher pitches per plate appearance rate really have? To find out I took a sample of team offensive statistics over the last five seasons from 2008-2012. I calculated the team’s average pitches per plate appearance and compared it with their win total, runs scored, on-base percentage and walk percentage to see if there was any correlation.

To determine how much pitches per plate appearance affected each stat I used linear regression, which is a way of mathematically determining if there is a trend between how the data lays out. The important part of linear regressions is the R-squared value. The higher the R-squared the more likely it is that there is a correlation between the two stats. An R-squared value of one-tenth is equal to ten percent of correlation.

The first two stats I looked into were the big picture stats, wins and runs. Below are graphs for wins and runs versus pitches per plate appearance, the R-squared value for both is listed on the graph.

Not surprisingly there is little correlation between pitches per plate appearance and wins and runs. Baseball is a complex game and just one small aspect should never have too big of an effect on these big picture stats. If there was a high correlation here you can bet that Billy Beane would be all over it for Moneyball II.

The next graph is for pitches per plate appearance versus on-base percentage.

This one was a bit more surprising to me as I thought there would at least be a small correlation between the two. But with an R-squared of only .027 that is obviously not the case, it is about equal to the correlation between wins and runs and pitches per plate appearance. Again, like with the other two, baseball is a complex game and a lot goes into on-base percentage.

So all of those stats were a little too indirectly related to the effects of a high pitches per plate appearance rate, so let’s narrow it down even more. This last graph is the relation between pitches per plate appearance and walk percentage.

Now that’s a good looking graph. Unlike the flatness of the first three graphs, this one has the start of the left-to-right upwards diagonal we are looking for. And the R-squared value confirms this as it as a nice .3 or 30% correlation. While that obviously means that pitches per plate appearance isn’t the biggest factor in walk rate, it still is a factor. When you think about it this makes sense. It takes four pitches to walk, which is more pitches than in the average at-bat. Therefore, players who walk often are seeing more pitches per plate appearance than average.

So pitches per plate appearance isn’t the wonder stat that will create the next revolution in baseball. However, it still suggests that a higher rate is beneficial to a team and individual player. With that in mind let’s see how the Nationals regulars, since this is a Nats blog, are doing so far this season. Here are the Nationals regulars ranked from lowest pitches per plate appearance to highest. Stats are taken through April 30.

While I am not a critic of Danny Espinosa, it is not altogether unsurprising that he has the lowest rate so far in this still young season. It is surprising to see Kurt Suzuki with the highest rate, and it’s not particularly close either, but he has been having some great plate appearances down in the eight hole. Perhaps it’s time to move him up higher in the lineup.

But that’s only how they rank on the team, for a little more context let’s compare them to the league average at their position.

There are five Nationals who see more pitches per plate appearance than the league average for their position: Kurt Suzuki, Adam LaRoche, Jayson Werth, Denard Span and Bryce Harper. This will likely be completely unsurprising to anyone who has watched the Nats this year, as all five have stood out in this regard. Outfield has the three highest league average pitches per plate appearance, but all three Nationals outfielders were still able to outperform their peers.

Middle infielders Danny Espinosa and Ian Desmond are helped by having the lowest league average pitches per plate appearance and both still are below league average. That hasn’t had too much of an effect on Desmond’s production though, as he has continued his offensive tear from last season. The other National below the league average at his position is Ryan Zimmerman and that is certainly surprising since Zimmerman is a smart and talented hitter. His rate is likely affected by the injury cutting into his playing time and it being early in the season.

The Nationals last season were 25th in pitches per plate appearance in 2012. The addition of Span and full seasons of Harper and Werth should certainly make that ranking rise in 2013. While seeing more pitches per plate appearance doesn’t guarantee success, it is still beneficial and the Nationals are set up to see more pitches this season.

If there's something here you would like to learn more about or you would like to see the raw data I used for this, let me know by sending me a message on Twitter, @nextyeardc.