BUENOS AIRES, ARGENTINA - APRIL 08:  Juan Martin Del Potro of Argentina celebrates  after winning against Marin Cilic of Croatia during the match between Argentina and  Croatia for the quarterfinals of the Davis Cup at Mary Teran de Weiss stadium on April  08, 2012 in Buenos Aires, Argentina. (Photo by Charly Diaz Azcue/LatinContent/Getty  Images)