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MLB: State of the Game- Pitching Roster Crunch

Article Summary: MLB Pitching is VASTLY different than it was years ago. Find out how different, the megatrend factors driving the changes, and how it can all impact the Astros in 2023.

The Key Question is- Do the Astros REALLY have enough pitching. Let's find out.

As I was putting the report cards for the Astros teams of the 1980s and 1990s, I noticed that the number of pitchers used on those teams was significantly lower than the recent Astros teams.

I knew this was not an issue unique to the Astros. It has been part of a league wide megatrend. To illustrate this trend, see the graphs below. I calculated the average number of pitchers used in a season by each team.

The data is grouped in five full season groups (1981, 1994, 1995, 2020 seasons were excluded). Over the 49-year span, the average number of pitchers used per team in a season has almost doubled!

The average team uses almost 28 pitchers in a season currently. TWENTY EIGHT! The Astros used 22 pitchers in 2022.

It seems to me there have been more position players used in blowouts than previously. Teams also use September callups to give prospects experience. Therefore, I decided to plot the average pitchers per that have more than 20 IP and essentially the trend line is the same.

The average team uses just over 18 pitchers who pitch more than 20 innings in a season currently. The Astros had 16 in 2022.

What is also interesting is to plot the number of pitchers who pitched more than zero innings and less than twenty innings.

This would include some September callups, players that got injured early (Taylor), pitchers that performed badly

(Baez), and position players used to close out games (none for the Astros in 2022).

The fact that the number of players 0-20 IP pitchers have nearly quadrupled is noteworthy.

My mind immediately wanted to find out why. I had excluded the COVID seasons so why was this trend going up and seemingly accelerating and were the additional pitchers mainly SP or RP?

Here is the plot of the number of pitchers who have started games per team over this same period. You can see that until the past five full seasons the average number of starting pitchers was essentially the same as it was 40 years earlier. Therefore, the trend until 2017 where teams are using more and more pitchers was exclusively adding more relief pitchers.

What has happened since 2017 to add 20% to the number of SP teams are using? This bump in SP is definitely part of the story in the acceleration of the overall of the number of pitchers deployed in the last full five seasons.

Why has the number of starting pitchers and the number of overall pitchers increased so dramatically?

Factor #1- OPENERS

In this period the Tampa Bay Rays started the phenomena we now know as the opener. This use of a RP to start the game basically renders the concept of SP for heavy opener teams as meaningless. It also caused the average IP of a start to drop by over a half an inning.

The rest of the trend on the drop of IP per start also explains the need for more RP.

Below is the Rays Opener data.

You can see the Rays utilized the opener heavily in 2018 and 2019. A mindboggling 61 games were "started" by Tampa Bay openers in 2018. You can see how this also increased the number of "starters" used by the Rays.

The Rays were not the only team that started using the opener during 2017-2022 but they were the most prolific. I believe most of the rise in the number of SP used above league wide is the advent of the opener and its spread to more teams in the MLB.

Factor #2- Six-man rotations

Many teams adopted six-man rotations in 2020 and/or 2021 to help manage load on starting pitchers post COVID. There was a concern about SP taking on a full SP load.

In fact, at the beginning of this 50-year period I am looking at many if not most teams were deploying 4-man rotations. The opener, six-man rotation, and the other factors have led to fewer games started per starting pitcher. This too dropped significantly in the past 5 full seasons.

Factor #3- Shorter starts by non-opener SP

In the data shown above not only did the number of SP grow in the last 6 years but the overall number of RP grew as much or more. The average IP per start dropped by over 0.5 IP BEFORE 2017. Since SP are not going as long as they did previously, more RP are needed to fill the gap.

All of these factors work together to cause more pitchers to be used per game.

1974-1976- 2.4 pitchers per game

2019, 2021-2022- 4.4 pitchers per game

Part of what has been happening here is the managers have data that shows most SP are worse the third time through the lineup than they were in the first two cycles. Data is somewhat driving the shorter starts as well.

Factor #4- 26-man active rosters

  • Rosters expanded to 26 in 2020. Covid rules in 2020 actually had 30-man roster early and then 28-man rosters after a month or so into that season.

  • In 2021, Rosters were 26 but teams were not limited to 13 pitchers so many teams actually carried 14 pitchers due to the same load management issues I mentioned previously. Rosters expanded to 28 on September 1st in 2021.

  • In 2022, Rosters were 26 and teams were limited to 13 pitchers. Rosters expanded to 28 on September 1st in 2022.

In this era, teams have been spreading the load and having pitchers exert max effort when they do pitch. Velocity has been prioritized over stamina.

Basically, what we have seen is if you give a manager an extra pitcher, they will use him.

Factor #5- Pitch Velocity and Usage Trends

The graphs on the left show the increase in average velocity for each pitch since 2008 (the statcast era for this data from

In 15 seasons the average pitch has increase 2.2 mph.

The largest increases in velocity have come on the curveball (76.5 to 79.5 mph) and the change-up (82.3 to 85,3 mph).

The largest increase in usage has come on the slider (13.9% to 20.8%).

Throwing a baseball two mph faster may not seem like much. However, sliders and change-up are thrown at speeds that pitchers 40-50 years ago threw their fastball. All of this illustrates the max effort and stress that pitchers are now throwing. THIS is a big part of why the stamina is down because the max effort is up. The stresses of throwing with this effort leads to the number of pitchers the modern game has.

Factor #6- Pitcher development and evaluation

The data I just showed you was not available publicly a generation ago. Now it is available for everyone to see. Teams have MOUNTAINS of pitch data and advanced metrics on pitchers as early as high school or in some cases earlier. This means that the development process is faster, and evaluations come earlier. Teams have FAR shorter leaches for their players that reach the majors because they know who the next man up is. This leads to a revolving door with AAA with pitchers and increase the number of pitchers a team uses.

Factor #7- Injuries?

I believe more and more pitchers are lost to injuries due to the effects of the max effort throwing. I know there is data out there, but I don't have it. I believe due to their younger age MOST of the Astros starting pitching has been somewhat muted from this injury affect and Astros fans have really been blessed from the carnage some teams have had to endure.

Putting it all together- what does it all mean?

The pitching trends all point to a potential challenge for the Astros. I recently showed this as the projected 2023 Astros pitching staff.

This table shows 21 pitchers in an environment where the AVERAGE team is using 27.8 pitchers per year.

This table shows 9/10 SP in an environment where the average team is using 11.9 starting pitchers per year.

Will the Astros be blessed with good health as they generally were in 2022? Now you know the background.

Pitching in the 2020s is VASTLY different than it has been at any point in the past. It is a war of attrition. Let's hope the Astros are fully prepared for it.

I thought the Astros had enough pitching. Maybe they need a LHRP still. After researching this, I am far less confident.

PLEASE COMMENT BELOW- with your questions and/or thoughts. What did you find most surprising in this data?

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Data for this article is from Fangraghs and Baseball Savant and Baseball reference.

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