The prehispanic ball game, known in Nahuatl as Ullamaliztli, has been played in what is modern-day Mexico since at least 1,200 BCE. This hip-ball game was prevalent throughout mesoamerican cultures, as courts have been found from Arizona to El Salvador. What probably began as a ritual tradition later became a political tradition, and in some cases an alternative to wars, before ultimately becoming a sport played solely for recreation (although in some areas and cultures, natives still kept the ritual aspect of it).
Although the hip-ball game was the most popular variant across all eras and cultures, there is evidence of other variations of the game existing, including a stick-ball game.
In this alternate timeline, this stick-ball game has transformed over hundreds of years. Nowadays, Tlaquicheros (throwers) lob a small rubber ball to Tlapalleros (strikers) who attempt to hit the ball in the air. The rules are the same as for our timeline's baseball (3 strikes for an out, 4 balls for a walk, etc.), but the terminology used is in Nahuatl and represents the historically ritualistic nature of the game, which was meant to encompass the duality of the universe (day and night, life and death, etc.)
In our timeline, the conquering Spanish banned the traditional ballgame due to its ritualistic nature. In this alternate timeline, this never happened, allowing the game to thrive and even partaking in it and infusing some influence from European games. (We won't go into the social, political or whatever other details of alternate timelines in this simulation. I just thought this would be an interesting backstory to begin a fictional OOTP league in Mexico and use it as an excuse to learn more about my own culture and history.)
Some amateur Ullamaliztli clubs formally began their activities during the peace of the 2nd Mexican Empire between 1864 and 1867. It was said that Maximilian I, who was known for promoting and preserving native culture, took up the game himself.
This period was immediately followed by Benito Juárez' presidency and then Porfirio Díaz' dictatorship from 1876 to 1911. Although the dictatorship proved to be an economically stable time, this came at the expense of the working class. The higher class preferred to practice European sports, such as football, as they were considered more prestigious. Díaz was overthrown in a bloody Revolution war that lasted 10 years.
The year is now 1935, following the Reconstruction period. Ullamaliztli remains a popular game amongst the working class, many of whom have mastered their craft. Exhibition games between the amateur clubs are watched by hundreds of visitors. Mexican entrepeneurs discuss the possibility of the creation of a professional league. This will enable them to charge visitors to watch the game, as well as paying the best players who would be able to focus solely on playing the game.