The Aztecs played one or more variants of a whole group of games that we collectively refer to as "The Mesoamerican Ball Game." At the time of the conquest, the Spaniards specifically referred to the game the Aztecs played as ulamalitzli, which is also often simply referred to as ulama (the Mesoamerican ballgame more generally is often referred to as tlachtli, from another Nahuatl word). This version of the game was played on a court, usually an I-shaped playing field between two banked stone structures. The banks would often hold tenons or rings, which are believed to have been used in scoring. The purpose of the game was for two teams to volley the ball back and forth between them using mainly their hips to strike the ball (in some variants, other body parts, such as elbows, might be used). It is believed (though by no means certain) that ball games were usually played between teams made up form elite, noble members of society, and that playing well was expected of high-status young men.

In the Aztec period (roughly A.D. 1425-1521), ballcourts were found in almost all communities of any size, and were widely distributed throughout Central Mexico (and beyond, but that is less relevant to the Aztec Empire).

The idea that someone (whether the losers, or the winners, or captives, or someone) was sacrificed at the end of the game is linked to various versions of the ballgame, including that played by the Aztecs. There is evidence for the sacrifice, by removing the heart and by decapitation, of ball players from iconography at Tajin and other sites in Veracruz State (Mexico's Gulf Coast) and at Chichen Itza and other sites in the Yucatan Peninsula, from earlier Periods (the Late Classic and Epiclassic, roughly A.D. 650-1150). There are numerous similar examples of iconography from across Mesoamerica in many time periods.

Bernardo de Sahagun, a Spanish priest who wrote accounts of many stories, beliefs, and practices of the Mexica and other peoples of the Aztec empire, described a sacrificial ritual in a ballcourt at a ceremony dedicated to the rebirth of the solar deity Huitzilopochtli.

Susan Gillespie argues that the sacrifice of people in the ballcourt by decapitation may be linked to a variety of Mesoamerican myths about decapitation and rebirth, which includes the Maya myth of the "Hero Twins," one of whom was sacrificed by the other in a ballcourt in the underworld in a complex plot to defeat the "Lords of Death," and the Mexica (Aztec) myth of Coyolxauqhi, the moon deity, who was dismembered by her brother Huitzilopochtli, possibly in a ballcourt. Like the decapitated Hero Twin, Coyolxauqhi is cyclically reborn and her death is reenacted. Gillespie argues that the nobles in the ballcourt were, at least some times, impersonating these and other deities and reenacting myths like these, requiring a sacrifice in order to continue the cycle. It should be stressed though, that it is far from clear who was sacrificed in these rituals. Presumably, the reenactor of the appropriate deity would be decapitated, but whether that person was one of the noble participants, a war captive, or some stand-in, is uncertain.

Sources: Gillespie, Susan D. 1991. Ballgames and Boundaries. In The Mesoamerican Ballgame, edited by Vernon L. Scarborough and David R. Wilcox, pp. 3-24. University of Arizona Press, Tucson.

Santley, Robert S., Michael J. Berman, and Rani T. Alexander. 1991. The Politicization of the Mesoamerican Ballgame and its Implications for the Interpretation of the Distribution of Ballcourts in Central Mexico. In The Mesoamerican Ballgame, edited by Vernon L. Scarborough and David R. Wilcox, pp. 317-345. University of Arizona Press, Tucson.

Wilkerson, S. Jeffrey K. 1991. And then they were Sacrificed: The Ritual Ballgame of Northeastern Mesoamerica through Time and Space. In The Mesoamerican Ballgame, edited by Vernon L. Scarborough and David R. Wilcox, pp. 45-71. University of Arizona Press, Tucson.