Players are wearing the number 21 in honor of Roberto Clemente Day, which Major League Baseball celebrates to commemorate the legendary Hall of Famer Roberto Clemente. On this day, all players, managers, coaches, and umpires wear a "21" patch on their uniforms to recognize Clemente's legacy. Additionally, players of Puerto Rican heritage, past Roberto Clemente Award recipients, and nominees for the award have the option to wear the number 21 on their uniforms during games. The Pittsburgh Pirates, the team Clemente played for his entire career, typically wear number 21 across the roster on this day as a special tribute. This tradition celebrates Clemente's remarkable achievements on the field and his humanitarian efforts off the field.