Astros: The Green Index

Let’s start with the headline.  The 2019 Houston Astros as they are currently structured are attempting to do something that the previous four World Series champions did not do.  The current projections for the pitching staff estimate that the Astros will ask players with less than one year of accumulated MLB service time to pitch 140% more innings than the average of the past four champions.  As an Astros fan this may or may not concern you; but before this season begins, you should understand this risk.

This projection could quickly change if the Astros acquire a number three veteran pitcher.  In previous Larry the GM articles, I have called for this. 

With this article I hope to help you understand a new metric: the Green Index.  The Green Index is a measure of how dependent your team is on less experienced players – i.e., how “green” is your team.

Before we get there, let’s understand what MLB Service time even means.  Per the official MLB website, here are a few basics

  • Each Major League regular season will consist of 187 days starting in 2018 (typically 183 days in previous years);
  • Each day spent on the active roster or disabled list earns a player one day of service time;
  • A player is deemed to have reached one “year” of Major League service upon accruing 172 days.

When you see service time listings they will typically be represented by years.days.  For example, a player with a 2.117 service time has been active or disabled for 2 years and 117 days.  To convert these to a decimal number to represent the true service time, one would take the 117 days and divide by 172 days (a service time year).  In this case the player would have 2+117/172, or 2.68 years.  

Now that we understand service time, how do the 2019 Astros project to allocate playing time vs. the service time of the players on the team?  For this, I have utilized depth chart projections from FanGraphs.  The current projections show three players not on the current 40-man roster to pitch in 2019.  As a side note, eight players not on the opening day 40-man roster either pitched or batted for the Astros in 2018.  The service time data is available most easily at Cot’s Baseball Contracts and at Baseball Reference. The service time shown here is as of opening day. 

This is a lot of data; here are different ways I have explored it.

Service Time

Given the data above, one may wonder whether this is a relatively experienced or inexperienced team.  This data shows that the opening day average service time of the 40-man roster in 2019 is 3.4 years.  For this I did not include the players projected to join the team during the season.   In the table below, I compare the OD average service time with the 2018 Astros and the last four World Series champions.  As you can see, this would project the 2019 team to be on par with most of the other champions.  Not surprisingly, a great team has a mix of veterans and younger players that play well.

Of particular note for Astros fans is that the 2017 team was very inexperienced to be winning the World Series.  In 2017, Alex Bregman, Gurriel (somewhat an anomaly in this analysis), and Musgrove delivered significant playing time with less than one year of service time.  It may also be hard to remember that Carlos Correa, Lance McCullers, and Devenski also had less than two years of service time. The 2017 Astros got heavy contributions from relatively inexperienced players.  The batters on the 2016 Cubs were also similarly inexperienced. 

As I considered the average service time of the 40-man roster statistic, I was not satisfied that it truly quantified the impact of inexperienced players on a team’s success.  A better measure would be to explore the impact of the innings pitched and plate appearances batted by inexperienced players.  Were these young players expected to play a lot?  That was truly the question. 

Less than one year and less than two years of service time: Innings Pitched

Also, the FanGraphs depth charts project that the 2019 Astros will have 440 innings pitched by players with less than one year of service time.  Because I gave you the conclusion first, you may think that seems like a lot of innings.   From the comparison to these other teams, it is an extraordinarily high number of innings for such inexperienced pitchers.  Looking at the data in detail also highlights that the pitchers are not mainly players like Rodgers that are close to one year of service time.  Most of these players are true rookies.

There are no innings projected to be pitched by players with more than one year of service time and less than two years of service time.   This is likely due to the 2018 rookie pitchers not having the playing time in 2018 because of a stacked pitching staff.

Less than one year and less than two years of service time: Plate Appearances

The depth charts project that the 2019 Astros will have 291 plate appearances by batters with less than one year of service time.  This would be on the low end of the teams listed.  Personally, I believe Kyle Tucker will have significantly more PAs than are currently projected. 

Overall, the 1166 plate appearances projected from players with less than two years of service time would still be on the lower end of this list.   This is a reflection that the Astros do not plan to have a lot of playing time for new batters.   

Green Index: Average weighted service time

After considering the data with both filters (Average of service time, IP/PA of inexperienced players), I decided to create an average weighted service time metric.  An illustration probably explains the system best.

For this example, we will take three pitchers and three batters.  In each case, one has 10 years of service time, one has 5 years of service time, and one 86 days (0.5 years- 86/172) of service time.  Let’s say the 10-year pitcher pitches 100 IP, the 5-year pitcher pitches 50 IP, and the 0.5-year pitcher pitches 30 IP.

To calculate the weighted service time, one multiplies the service time by IP for each player, as shown below.  Then one adds the products (1265 in this case) and divides by the total IP (180 in this case).   In this example, the three players have an average service time of 5.17 but a weighted service time of 7.03.  

I show a similar example for batters, using the plate appearances of the three batters.

These weighted service times are a more accurate metric for the degree of “green” a team has.   Above, we discussed a Green Index.  As shown in this example, the Green Index is just the average of the Weighted Average IP Service Time (7.03) and the Weighted Average PA Service Time (7.28).   So how does the example Green Index of 7.15 compare to the teams I showed?

Here is the summary table again now that you understand what the Green Index means.

Despite the high number of projected IP of inexperienced pitchers, the overall Green Index of the 2019 Astros is right on par with the previous few champions.  If one had the time, they could calculate the Green Index of all franchises over the history of baseball.  I think we would find historically the 2015 Royals (5.7) are far more typical than the 2017 Astros (4.2).

What does it all mean?

While the Astros are heavily dependent on several pitchers with less than one year service time (barring a trade or free agent signing), their overall Green Index is on par with other recent champions.  So relax and enjoy the ride.

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