MANY
Currently, no player wears #21 for the Yankees.
Corey Jones wears No. 21 for North Melbourne Football Club Cameron Mooney wears number 21 for Geelong. Jason Akermanis wears No. 21 for the Western Bulldogs. Quinten Lynch wears number 21 for the West coast Eagles. Daniel Merrit wears No. 21 for Brisbane. GO LIONS
Mike Jenkins (CB) currently wears number 21 for the Dallas Cowboys.
Eric Wright currently wears the #21 jersey.
Mike Jenkins
Marcus Camby but he got traded
Tim Duncan
The number isn't being worn by anyone on the Yankees' 2010 roster.
Lucasz Fabianski wears the number 21 on his shirt
When he was a timberwolf he was #21. Now he is #5 with the celtics.
Borje Salming wore number 21 for the Toronto Mapleleafs. However, he left the team in 1989 and his number 21 was taken by a future NHL star named Sean McKenna.
Currently, there is no player who wears #21 for the Seattle Seahawks.