why do the blue jays have 21 on their jersey

The Toronto Blue Jays have the number 21 on their jerseys as a tribute to Roberto Clemente Day, which is celebrated by Major League Baseball on September 15. On this day, MLB honors the legendary player Roberto Clemente by having all players, managers, coaches, and umpires wear a "21" patch on their uniforms, as well as allowing players of Puerto Rican heritage, past Roberto Clemente Award recipients, and the season's award nominees the option to wear the number 21 on their jerseys. This tradition commemorates Clemente's remarkable career and humanitarian legacy. The Blue Jays, for example, have several players and personnel wearing No. 21 or a patch in his honor during this observance.