Federer ends Djokovic streak

Roger Federer got one over on world number one Novak Djokovic as the Swiss great booked his World Tour Finals last four spot with a straight sets victory on Tuesday.

Federer triumphed 7-5, 6-2 in their group stage clash in the packed O2 Arena in London, to hand the Serb his first indoor defeat in 39 matches -- a streak stretching back to 2012.

But after becoming the first man through to this year's semis, Federer insisted Djokovic was still the favourite to win the season-ending tournament, which is disputed between the top eight players, divided into two groups.

Earlier in the same group of four, Japan's Kei Nishikori gave his hopes of reaching the semis a major boost with a 7-5, 3-6, 6-3 victory over Tomas Berdych.