Here's why it would be a bad idea for MLB to retire Roberto Clemente's No. 21
Pirates wear No. 21 to honor Roberto Clemente
Puerto Rican Twins don No. 21 in tribute to Roberto Clemente – Twin Cities
All Pirates Wearing #21, Rest of MLB Wears Patches in Honour of Roberto Clemente – SportsLogos.Net News
Altoona Curve honors Pirates legend Roberto Clemente, retires No. 21
Uniform number (Major League Baseball) - Wikipedia
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