Mariano Rivera Number 42Mariano Rivera is the last Major league ballplayer, and Yankees player still wearing uniform number 42. Major League Baseball retired Jackie Robinsons uniform number 42. No Other player on any team can wear the number. Because Mariano had the number when Robinsons number was retired he was allowed to continue wearing it. When Mariano Rivera retires from Baseball the New York Yankees will retire uniform number 42 in honor him.