Mookie Betts wore the number 21 jersey as part of MLB's celebration of Roberto Clemente Day, which occurs every September 15. Betts, being a nominee for the Roberto Clemente Award, was permitted to wear number 21 in honor of Roberto Clemente, a Hall of Famer and legendary Puerto Rican player. MLB allows nominees and previous recipients of the award, as well as Puerto Rican players, to wear the number 21 jersey on this day out of respect for Clemente's legacy. This number is traditionally associated with Clemente, who made a profound impact on the game and community. Betts was honored as a nominee for the award and wore the jersey during games around this celebration.
