Following the game, the jerseys will be auctioned off with all proceeds going to the Clemente Foundation and Pirates Charities.
"Since 1973 the only persons allowed to wear No. 21 in a Pirate uniform would had been any of the three sons. I became the closest to have that honor, but didn't continue to play to reach the Major League level," said Luis Clemente. "History will be made this September 9 and we would like to express our deepest gratitude to Derek Shelton for his initiative and supporting the Clemente Family endeavors. We thank Bob Nutting and the Pirates organization for continuing the goodwill of the Clemente name in their community efforts."
Clemente died in a plane crash Dec. 31, 1972 while attempting to deliver a relief package to Nicaragua after a devastating earthquake in its capital city of Managua. One of baseball's greatest humanitarians, Clemente made 15 All-Star teams and two World Series championships during his career with the Pirates. The Baseball Hall of Fame elected Clemente to the class of 1973, allowing him to forgo the typical waiting period after his death.
No Pittsburgh player has worn Clemente's No. 21 since his death.
"Our staff and players are excited to wear the number 21 with pride as we constantly search for ways to not only honor Roberto's legacy but to keep his memory alive through our community actions," said Pirates Chairman Bob Nutting. "We recognize what this moment represents for all of us within the organization, the Clemente Family, our fans, and the people of Puerto Rico. We take great pride in representing such a great ambassador of the game."
Major League Baseball has celebrated Roberto Clemente Day for each of the last 18 seasons.