Starting from this season, the following format changes were implemented: • The tournament was expanded from 38 to 47 teams. • A total of 10 teams eliminated from the Copa Libertadores (two best teams eliminated in the third stage of qualifying and eight third-placed teams in the group stage) were transferred to the
Copa Sudamericana. • The schedule of the tournament was extended to year-round so it would start in late January or early February and conclude in late November or early December. Although CONMEBOL proposed to change the format of the final to be played as a single match at a venue to be chosen in advance, they later decided to keep the two-legged home-and-away format. On 18 November 2016, the
Liga MX president Enrique Bonilla announced that teams from
Mexico would not participate in the 2017 Copa Libertadores due to the format change which put it in conflict with the Mexican league schedule. However, he left open the possibility of a return as soon as 2018 if a solution was found. Initially CONMEBOL announced that the tournament would be expanded from 38 to 44 teams, and the additional six berths would be distributed to the Copa Sudamericana champions (which no longer occupy one of the places allocated to their association and are now allocated an additional berth), two to Brazil, and one each to Argentina, Chile and Colombia, based on commercial and sporting criteria. Following the withdrawal of teams from Mexico, CONMEBOL announced that the other six associations (Bolivia, Ecuador, Paraguay, Peru, Uruguay and Venezuela) would also be each allocated an additional berth, further expanding the tournament to 47 teams. From this season, the Copa Libertadores champions (which no longer occupy one of the group stage places allocated to their association) and the Copa Sudamericana champions gained direct entries into the group stage, meaning a total of 28 teams (increased from 26) would directly enter the group stage, while the other four berths (decreased from six) would be decided by the qualifying stages. The group stage berths left vacant following the withdrawal of teams from Mexico would be redistributed to Argentina and Brazil. For the qualifying stages, a total of 19 teams (increased from 12) competed in three rounds where the four winners advanced to the group stage (initially 16 teams would compete in two rounds before further expansion following the withdrawal of teams from Mexico). ==Teams==