Serena Williams of the USA plays Kim Clijsters in the semi finals at the US Open Tennis Championships in New York

Serena Williams of the USA reacts after a point in her semifinal match against Kim Clijsters of Belgium in Arthur Ashe Stadium at the US Open Tennis Championships at the Billie Jean King National Tennis Center in New York on September 12, 2009. Clijsters defeated Williams 6-4, 7-5. UPI/John Angelillo