Before the #21 became synonymous with Tim Duncan, another player made a case for having the number retired.
Alvin Robertson was a force. During the dark era of the Spurs, Robertson was a beacon of hope during four Spurs losing seasons in the mid to late 80s.
Robertson is one of only four NBA players to earn a quadruple-double. Of the other three (Nate Thurmond, Hakeem Olajuwon, and David Robinson), Robertson is the only player to do so as a guard. He also hit the double-digits in points, assists, rebounds, and steals. The big men earned their fourth category on blocks versus steals.