Should the Pittsburgh Pirates trade patience for power?

Would the power-hungry Pittsburgh Pirates truly benefit from a more aggressive approach?

While doing research for this week’s in-depth Pittsburgh Pirates study, I stumbled upon an interesting article by Ryan Pollack over at The Hardball Times.

The piece quantified and analyzed the aggression of hitters based on their “swing zone,” or the area that hitters are willing to offer at pitches. Pollack terms this metric the “Aggression Factor” of a batter.

What is interesting about this “Aggression Factor” is that it allows us to compare batters not based on a theoretically perfect strike zone, like O-Swing% and Z-Swing%, but rather based on the actual size of the zone that the players are swinging at. So with this metric, a batter that is very aggressive, going after pitches all over, would have a high Aggression Factor. Another player who prefers to only swing at pitches they are confident they can hit, would have a relatively low Aggression Factor

Defining Aggression Factor

Using Pollack’s definition, we can find the Aggression Factor using Statcast data for each pitch that a given player swung at, regardless of contact by following these steps.

  • Find the median absolute deviation of each pitch offered at along both the horizontal (x) and vertical (z) axis.
  • Multiply both of these numbers together giving us the square footage of the player’s median swing zone. This is where I slightly deviate from Pollack’s analysis, Pollack prefers to put these numbers into terms of inches rather than feet, since most Statcast data is in terms of feet, I prefer using the square footage measure. That being said the information contained within is the exact same just in different terms, so it’s really just a matter of preference.
  • Divide by the player’s total number of swings to normalize the scores over different playing times then multiply by 100.

And that’s it.

To think about what exactly this metric means, let’s take two examples of Pittsburgh Pirates hitters with different plate disciplines this year, Gregory Polanco and Andrew McCutchen.

What you’re looking at is the location of pitches that Polanco and McCutchen swung at this season from the catcher’s perspective.

If you look at the differences between the two charts, you can start to understand what exactly this Aggression Factor represents. The black boxes represent each player’s respective “swing zone”; for one Polanco’s is much bigger than McCutchen’s meaning that Polanco is much more aggressive than McCutchen.

While part of this increased aggression is due to the fact that Polanco has a larger strike zone than McCutchen, and thus has to cover a larger area, the only explanation for why the bottom of Polanco’s swing zone would be lower than that of McCutchen’s is that Polanco is just more aggressive.

Additionally, if we look at the concentration of swings, McCutchen’s is much denser around his swing zone, whereas with Polanco there is not nearly as clear a density around his swing zone.

So players with tighter swing zones, like Andrew McCutchen, would have a smaller Aggression Factor than someone like Gregory Polanco.

This is important because, ostensibly, a player that waits for their pitch will make better contact more often and perhaps even walk more often, than a player that does not.

Applying Aggression to the Pirates Players

Now that we have our aggression defined and hopefully conceptualized we can look at how the Pittsburgh Pirates hitters did this season against some inclusive hitting metric, in this case wRC+.

For this cart, I only listed Pittsburgh Pirates hitters who are likely to return for next year; additionally I set a somewhat arbitrary minimum of 100 swings, to hopefully gain significant data on the player’s actual swing zones.

From this chart there is a pretty clear negative correlation between increases in aggression and the value of a batter, meaning as batters expand their zone, their performance decreases.

It is also interesting just how predictive of wRC+ a batter’s aggression is. Aside from Luplow, Rodriguez, Diaz and Moroff, all players with relatively few swings for the Pirates this season, McCutchen was really the only player who significantly deviated from the blue trend line.

What this tells us is that a pathway to offensive success might be in the Pirates batters becoming more selective in the pitches they swing at. For one this would mean the Pirates would be making opposing pitchers throw them balls they can. Secondly, it would mean that the pitches the Pirates do swing at would have a higher likelihood of being productive offensively, given that it was where they want it.

These findings are consistent with that of the Pollack article, which found an overall downward trend in batter performance with increased aggressiveness.

Two key things to highlight from this graph is the patience of Josh Bell and Adam Frazier. The two rookies make up 2 of the top 5 most patient batters that the Pirates have. As those two continue to grow and mature as Major Leaguers, it’s likely that they will become even more selective with the pitches they swing at and, thus, even more productive hitters.

Aggressiveness on Total Offense

Another thing we may want to look at is where the Pittsburgh Pirates stack up relative to the rest of the league. Since wRC+ becomes a bit less meaningful on the team level, we’ll be using wOBA, which is the base statistic of wRC+.

This chart is interesting because, while it shows the downward trend of aggressiveness and offensive performance that we should expect based on what we viewed previously, it also shows Houston, the league’s most productive offense was 6th in aggressiveness, but the 7th most aggressive team, the Padres, was the second worst team offensively.

The Pirates were in the middle of the pack in terms of aggressiveness this year, but well underperformed the trend for wOBA. From this macro-standpoint it is very difficult to say if the Pirates as a team would have benefitted from any more or less aggressiveness; however, since it was so clearly shown on the micro-level that improving individual batter’s patience improves their outcomes, I doubt decreasing aggressiveness would hurt the Pirates overall offense in any way.

Aggressiveness on Home Runs

The Pirates lack of home runs, despite a league wide jump in homeruns, was an area of concern for many Pirates fans and writers alike.

Given that home runs do seem to becoming a larger part of team offense, here is the chart of aggressiveness and Home Runs hit.

There is a slight positive correlation between increasing aggressiveness and increasing home runs. That being said, as I wrote in an article from a few weeks ago, the Pittsburgh Pirates’ offensive issues this year didn’t spring from a lack of home runs, but rather a lack of every kind of hit.

Additionally, aggression has no statistically significant impact on overall power as measured by ISO; meaning that teams that are more aggressive and hit more home runs, do not see their overall extra base numbers improve. As such, increasing aggressiveness, which has an overall negative impact on offensive production, has only a marginal benefit of more home runs hit but at the expense of doubles and triples, so it doesn’t make much sense for the Pittsburgh Pirates Pirates to increase their aggressiveness at all.

Buck the trend

What’s interesting is that this all seems to run counter to what we are seeing in league wide-trends; players are becoming more aggressive and more home runs are being hit, not less aggressive and more productive. This could mean that teams have found some disproportionately large value in home runs; for instance home runs may increase the probability of winning exponentially more than any other form of hit, relative to their likelihood. However, if this is true, I have not seen the research to suggest it, for whatever that’s worth.

Alternatively, it may be that a market inefficiency is opening up in baseball, the market for patient hitters. A hitter who quietly generates positive offensive value for a baseball team may end up receiving less in free agency versus their home run hitting counterpart this offseason given this league wide push for more power. This could serve as a point of exploitation for the Pirates to win cost effectively in 2018 and beyond.

While being patient and waiting for good pitches is arguably the least sexy way of improving a team, it’s pretty clear that increasing player patience is a simple means of bettering an offense by getting more out of each player. As such, patience at the plate could be the signature of a successful Pittsburgh Pirates offense in 2018.

Nate Werner

Nate Werner is a senior at Penn State, where he is studying for his B.S. in Economics. He is a lifelong Pirates fan that uses the tools of statistical analysis to dive deeper into the numbers of baseball. His goal is to take the style of analysis used in front offices across the Major Leagues and bring it to the computer screens of everyday fans. You can read some of Nate’s more general analyses of baseball on and follow him on Twitter @GoldBoxStats.