Novak Djokovic has joined Roger Federer in the last four of the ATP World Tour Finals with victory over Tomas Berdych in London.
The world No. 1 required just one set to qualify but won his final group match 6-3 7-5 to secure a semi-final tie against Rafael Nadal. Berdych managed to recover an early break of serve, but Djokovic moved ahead again and clinched the set he required after 42 minutes.
The 30-year-old Czech rallied round and gave a good account of himself in the second set, but saw his serve broken at 5-5 and his Serbian opponent never looked back.
Andy Murray and Stan Wawrinka will play for the remaining semi-final place at 8pm on Friday.