Ever Wonder Why It Feels That You Can’t Keep Up With Major League Baseball Players Anymore?
April 2018: I have updated the data and charts used in this story with data up through the 2017 MLB season. You can view and interact here (use a computer. This is not optimized for mobile devices): https://public.tableau.com/profile/carleton#!/vizhome/NumberofDistinctMLBPlayersvsYear/Story
Today I was nosing around with the all of Major League Baseball’s historical data set (graciously compiled by Sean Lehman) when I noticed something really interesting: Almost every year, the League sets new records for unique players playing in games…and has done so for decades.
I made a chart noting the unique player IDs present in each season’s Appearance stats, which covers whether a player was in the game as a batter or defensive player (including Pitcher) for at least 1 pitch. :
If you would like to play with the data yourself, please use my Tableau Viz
The data set covers every Major League Baseball game from 1871–2015. It also includes some competing leagues that were eventually absorbed into MLB, like the Union Association and the American Association, both of which were later disbanded as their better clubs joined the American or National Leagues. So, when they joined, their player stats came over as well.
See the jump in players from 1968 to 1969?
Four expansion teams joined Major League Baseball for this season: the San Diego Padres, the Kansas City Royals, the Seattle Pilots, and the first MLB team in Canada, the Montreal Expos. To accommodate the additional teams, the two leagues were split into two divisions of East and West.
So, let’s move to a more modern era, say 1970 and on:
Now that’s more like it. And there is still a remarkable trend. From 1970 to 2015, unique player count increased 60%, from 840 to 1,343!
Notice the dip in 1994? There was a strike during that season starting on August 12. The work stoppage lasted 232 days, making it the longest such stoppage in MLB history. But, in 1995, things picked up where they left off.
The trend is obvious to the eye. Here is how it is described:
The results are statistically significant with a p-value of less than 0.0001 and R-Squared value of 96%.
Is the increase due to one class of player or all classes?
This trend had me wondering, “Were all player positions being changed out so frequently or was it one particular class of player?” After running a few filters I quickly saw the answer. It was the Pitchers. Pitchers come in and out of the League more than any other class of players:
In 2015, there were 735 different pitchers playing in MLB games! That is slightly more than double the count in 1970. And based on the trend, I expect a similar increase over the next few seasons.
The next question I had was, “What about the other players?”. So, I filtered out the pitchers and showed data from all of the other positions including the Designated Hitter (“DH”, who’s only job is to bat in place of the pitcher when it’s his turn in the lineup).
There is a definite trend upwards, but not nearly as with all of the positions or the Pitchers alone. In fact, over the last 20 seasons (1996–2015, inclusively), the count of distinct players has been hovering between 591 and 640, which is pretty darn flat:
Let’s look at Pitchers during that same 20-year span:
2015 saw 735 pitchers take the mound.
SEVEN HUNDRED and THIRTY FIVE.
Let that sink in for a sec.
1871: 19 Pitchers
1970: 363 Pitchers
2015: 735 Pitchers
There were 1,342 different players playing MLB in 2015, 735 (55%) of them were Pitchers.
That may explain why it’s so hard to keep up with all of the players in Major League Baseball.
UPDATE (6 JAN 2017):
The data for the 2016 season has been added to the database. Guess what? Even more pitchers!
While in 2015 and 2016 the total number of distinct players remained the same in back-to-back years for the first time since 1944 and 1945:
There were 7 more pitchers than in 2015:
