I'd have to go with Rivera. While Jackie definitely influenced the game for African Americans, Rivera edges him out in talent and an extensive, historic, and consistent career. No disrespect to Jackie, who is one of the greatest of all time along with Mo, but I just think Mo wins
Jackie Robinson changed baseball forever as the first African-American to play in Major League Baseball in the modern era. Mariano Rivera was simply a relief pitcher with great stuff who had the most saves in a career. A baseball player with copious saves is commonplace in the game today. Players of Robinson's character are rarely found anymore.
Mariano Rivera was clutch in the post season but you are comparing him to one of the biggest names in history. Jackie Robinson touched more lives and did more for the sport of baseball than Mariano Rivera ever did. This is not a knock on Rivera, just a statement of history.