Nats DH Cruz, other Clemente Award winners wear '21' on caps - The San Diego Union-Tribune
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Rays Star Calls Wearing No. 21 on Roberto Clemente Day 'An Honor
Some MLB Players Wearing #21, All Wearing 21 Patches Today for Roberto Clemente Day – SportsLogos.Net News
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Peter Dreier, Robert Elias - Baseball Rebels - The Players, People, and Social Movements That Shook Up The Game and Changed America-University of Nebraska Press (2022), PDF, American Civil War
Nats DH Cruz, other Clemente Award winners wear '21' on caps
Roberto_Clemente
Roberto_Clemente
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Roberto Clemente Award winners to wear cap patch
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Why are MLB players wearing 21? Tributes around the league for Pirates legend explained
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