Novak Djokovic did double duty on Wednesday in Madrid to lead Serbia into the semi-finals of the Davis Cup Finals. Djokovic defeated Alexander Bublik 6-3, 6-4 in singles and quickly returned to the court to partner Nikola Cacic to a 6-2, 2-6, 6-3 victory against Andrey Golubev and Aleksandr Nedovyesov,