The Avatar Selection screen appears at the start of all Sports Champions competitions. It allows the player(s) to select which Player Avatar(s) they want to use for the upcoming competition. Anywhere from one to four Avatars can be selected, depending on which Sport, which playing mode (Champions Cup, Free Play, or Challenge modes), and the number of Players. In addition to selecting the Avatar(s), it also allows the player to choose from available Outfits and Equipment.
Note that if you play multiple matches of the same Sport, the Avatar Selection is only available at the start of the first match. To change Player Avatar(s), you must exit the sport to the main Sport Selection screen.