The Philadelphia Phillies are wearing number 21 today to honor Roberto Clemente Day, which is celebrated annually around September 15. Major League Baseball observes this day by having all players, managers, coaches, and umpires wear a patch with the number 21 on their uniforms to commemorate the legacy of Roberto Clemente, a Hall of Famer and humanitarian who wore No. 21 throughout his career. Additionally, players who are nominees or previous recipients of the Roberto Clemente Award, as well as players of Puerto Rican heritage, have the option to wear No. 21 as their uniform number during games on this day. This tradition celebrates Clemente's contributions both on and off the baseball field, including his outstanding career and his humanitarian efforts that ultimately led to his tragic death while delivering aid to earthquake victims in 1972.