Novak Djokovic completed a 100 percent round-robin record at the ATP World Tour tennis Finals with a 6-2 7-6 defeat of Czech Tomas Berdych to book his place in the semi-finals.
The Serb followed his defeats of Jo-Wilfried Tsonga and Andy Murray with another clinical performance guaranteeing top spot in Group A.
The world number three Murray will join Djokovic in the semi-finals as long as the Briton avoids losing to Tsonga in straight sets in the evening match.
Roger Federer has already reached the semi-finals from Group B.
